Ford 6.0 L Engine, 6.4L Engine, 6.7L Engine, 7.3 L Engine, EGR Valve Testing

Crank Ventilation System:

6.0 L Diesel Engine: Emission

Closed Crankcase Ventilation (CCV) System:

The Closed Crankcase Ventilation (CCV) system
route’s crankcase blow-by gases from the breather assembly back into the engine
intake airflow to be used for combustion.


6.4 L Diesel Engine:

Closed Crankcase Ventilation (CCV) System:

The Closed Crankcase Ventilation (CCV) system
route’s crankcase blow-by gases from the breather assembly back into the engine
intake airflow to be used for combustion.

6.7 L Diesel Engine:

Crankcase Ventilation:

The crankcase ventilation system, Fig. 43, purges crankcase
gases to the intake manifold. The crankcase ventilation system consists of five
main elements, (1) expansion chamber separator, (2) cyclonic oil separator unit
w/integral pressure limiting valve, (3) stainless steel check valve, (4) oil
collection chamber and (5) pressure regulating valve.

Fig. 43 Crankcase ventilation system operation. Ford 6.7 L
diesel engine:


Combustion blow-by gases enter the rear port of crankcase vent assembly and pass
into an expansion chamber where larger oil droplets fallout of blow-by gases
due to a rapid decrease in flow velocity. The remaining blow-by gases flow through
into cyclonic oil separator unit. The blow-by gases are then separated into smaller
cyclone oil separators, which force smaller oil droplets to the side walls, so
they drain out and flow to oil collection chamber. The remaining lighter gases flow
to the intake manifold.

The oil collection chamber has a drain port and a stainless
steel check valve. The check valve allows smaller oil droplets to return to
crankcase while blocking gases in the oil return path. The oil separator works
using cyclonic technology. Therefore, no filter media is required inside
the canister. There is an integrated pressure regulating valve on the side of the
cyclonic oil separator which prevents excessive vacuum levels from being
applied to the crankcase. Maintenance is not required, and the canister is replaced as
an assembly.



Diesel Exhaust Fluid (DEF) System:

6.7 L Diesel Engine:

Reductant Heater & Sender Assembly:

The reductants heater and sender assembly contain a pickup
tube for reductants pump module, an electric heating element, a reductant’s
temperature sensor and an electrode type level sensor. The heating element is
directly above pick-up-tubes inlet filter. When the reductant’s temperature
the sensor detects the diesel exhaust fluid temperature dropping to the freezing
point of 12°F (-11°C), the PCM will command the glow plug control module to
provide voltage to the heating element. The heating element thaws liquid reductants
within the reductants heater and sender assembly reservoir during cold ambient
temperatures.The reductants level sensor incorporates four stainless
steel electrodes, with three electrodes, arranged vertically to provide a high,
middle, and low-level signal. The fourth electrode acts as a ground. When the
reductant’s tank is full, DEF closes a circuit between all three-level
electrodes and ground electrode, indicating tank is full. As DEF is consumed,
the level drops and uncovers each electrode in sequence. The PCM calculates DEF
level based on these signals.

Reductant Heaters:

The reductant heaters maintain DEF in a liquid state during
cold ambient temperatures. There are three heating elements in the system, each
receiving a voltage from the glow plug control module. The reductant tank heater
is integral to the reductant heater and sender assembly. The reductant pump
the heater is integral to the reductant pump assembly.

Reductant Injector:



The reductant injector, Fig. 44, is a pulse width modulated
solenoid controlled directly by PCM. The injector receives DEF from reductant
pressure line and sprays it into the exhaust stream, where it is mixed with
exhaust gases before entering SCR catalyst.

Fig. 44 Reductant injector components & location. Ford
6.7L diesel engine:







Reductant Pressure Sensor:

The reductant pressure sensor provides feedback to PCM, which
regulates system pressure by controlling pump speed using pulse width
modulation. The reductant pressure sensor is integral to the reductant pump


Reductant Pump Assembly:

The reductant pump assembly contains a diaphragm pressure
pump, a pressure sensor, a purge valve, an outlet filter and an internal
heating element. The reductant pressure sensor provides feedback to PCM, which
regulates system pressure by controlling pump speed using pulse width
modulation. When PCM request’s reductant injection, the reductant injector
opens and the pump operates, filling reductant pressure line and injector and
purging air from the system. When all air is purged, injector closes and pump
builds pressure to 73 psi. (500 kPa). The system is then primed, and injector
provides DEF to the SCR catalyst as determined by PCM.

When the vehicle is shut down, PCM closes injector and
actuates reductant purge valve, causing the pump to reverse flow and bleed down
pressure on reductant pressure’s lines. The PCM then opens injector to allow
gas to enter reductant pressure line, which in turn allows the pump to purge
all remaining DEF from the system and return it to the reductant tank. The PCM
closes injector and returns purge valve to the forward position. The PCM
commands the glow plug control module to provide voltage to the reductant pump
assembly internal heating element when reductant temperature approaches 12°F

Reductant Purge Valve:

The reductant purge valve allows the reductant pump assembly
to reverse flow and purge system when requested by PCM. The reductant purge
valve is integral to the reductant pump assembly.

Diesel Oxidation Catalyst (DOC):

6.0 L & 7.3 L Diesel Engines:


The purpose of the exhaust catalyst and exhaust system, Fig.
29, is to convey the exhaust gas from the engine to the atmosphere and reduce
the tailpipe emissions of hydrocarbon (HC), carbon monoxide (CO), oxides of
nitrogen (NOx) and diesel particulates.

The exhaust gas and particulates are directed away from the
engine through the exhaust manifold. The exhaust gas concentrations are then
reduced to acceptable levels as the exhaust gas passes through the Diesel
Oxidation Catalyst (DOC). Since the particulates are components of the exhaust
gas, some soot particulates may deposit on the DOC. The reduced emissions
exhaust gas and any remaining particulates flow through the muffler and
tailpipe into the atmosphere.

The converter body should be inspected for distortion and
other types of damage. Excessive heat can bulge or distort the converter or
filter. Furthermore, inspect for missing or improperly installed converter heat

6.4 L Diesel Engine:

Diesel Particulate Filter (PDF):

The DPF, Fig. 45, collects soot and ash particles that are
present in the exhaust gas of diesel engines. The DPF assembly typically consists
of active precious metals deposited on a substrate filter. The exhaust gas is
forced to flow through walls of porous substrate and exit through adjoining
channels. The particulates that are larger than the pore size of walls are trapped
for regeneration. During regeneration temperature in DPF increases to be
greater than 1022°F (550°C); at this temperature, soot in DPF burns and becomes
ash. The precious metal coating promotes regeneration of trapped particulates
through heat-generating reaction and catalyzes untreated exhaust gas. The
substrate filter is held in the metal shell by a ceramic fiber support system.
The support system makes up size differences that occur due to thermal
expansion and maintain a uniform holding force on substrate filter.


Fig. 45 Catalytic Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) & exhaust system. Ford 6.4 L diesel engine:










Diesel Particulate Filter (DPF) Pressure Sensor:

The DPF pressure sensor is an input to PCM and is used to
measure pressure before DPF. The sensor is a differential type sensor that is
referenced to atmospheric pressure. At key On, engine Off DPF pressure sensor
pressure value reads 0 psi. (0 kPa). The range of the sensor is 0 to 11.6 psi.
(0 to 80 kPa).

The converter body and diesel particulate filter should be
inspected for distortion and other types of damage. Excessive heat can bulge or
distort the converter or filter. Furthermore, inspect for missing or improperly
installed converter heat shields.

6.7 L Diesel Engine

Diesel Particulate Filter (DPF)

The diesel particulate filter, Fig. 46, collects soot and
ash particles that are present in the exhaust gas of diesel engines. The diesel
particulate filter assembly typically consists of active precious metals
deposited on a substrate filter. The exhaust gas is forced to flow through
walls of porous substrate and exit through adjoining channels. The particulates
That is larger than the pore size of the walls are trapped for regeneration. During
Regeneration temperature in the DPF increases to be greater than 1022°F (550°C).
The precious metal coating promotes regeneration of trapped particulates
through heat-generating reaction and catalyzes untreated exhaust gas. The
substrate filter is held in a metal shell by a ceramic fiber support system.
The support system makes up size differences that occur due to thermal
expansion and maintains a uniform holding force on the substrate filter.

Fig. 46 Diesel Particulate Filter (DPF). Ford 6.7L diesel engine:


The converter body and diesel particulate filter should be
inspected for distortion and other types of damage. Excessive heat can bulge,
distort the converter, or filter. Furthermore, inspect for missing or
improperly installed converter heat shields.

Diesel Particulate Filter (DPF) Pressure Sensor:

The diesel particulate filter pressure sensor is an input to
CM, and measures pressure before DPF. The sensor is a differential type sensor
that is referenced to atmospheric pressure and is located in the exhaust system
downstream of DPF. At key On, engine Off, the DPF pressure sensor pressure
value reads 0 psi. (0 kPa). The range of the sensor is 0 to 11.6 psi (0 to 80
kPa). The PCM calculates the soot load based on DPF pressure and initiates
regeneration when the soot load reaches the specified limit.


EGR System:

Diesel Engine EGR Valve System

With engine at normal operating temperature, the vacuum should be applied to the EGR valve at idle speed.

  1. Ensure all vacuum hoses are properly routed,
    securely attached and undamaged.
  2. Disconnect and plug EGR vacuum supply hose at
    EGR valve.
  3. Connect a suitable hand-held vacuum pump to
    EGR valve vacuum port, then gradually apply 12 inches of vacuum.
  4. Observe vacuum gauge on vacuum pump for loss
    of If a loss is present, replace the EGR valve.
  5. Release vacuum of the EGR valve and listen for
    the sound of valve hitting the seat.

6.0 L Diesel Engine

EGR Valve:

The EGR system reduces peak combustion temperatures and NOx.
The EGR valve, Fig. 47, is an electromechanical device that uses a linear
actuator to control the relative position of the valve pintle. This device also has
a built-in pintle position sensor that functions to provide PCM with a feedback

Fig. 47



EGR valve location. Ford 6.0 L diesel engine:

Inspect the system for proper installation of EGR valve,
control switches, and sensors. Inspect for proper connection of electrical
connectors and mechanical linkage.


EGR Actuator & Valve Position Sensor:

The EGR actuator is a variable position valve that controls
the amount of exhaust that enters the intake manifold. The EGR actuator is
controlled by PCM using a pulse width modulated signal that varies from 0-100%.
The EGR actuator consists of two components, a valve with an actuator and a
position sensor to monitor valve movement. The EGR valve position sensor is a
potentiometer sensor, which is needed to give control circuit feedback to
achieve the desired travel position. When the EGR receives a 5-volt reference
signal and a ground from PCM, a linear analog voltage signal from the sensor indicates
the position of EGR valve. Input signals from the manifold absolute pressure,
Exhaust pressure and BARO sensors are used by PCM to determine the EGR system

EGR System Cooler:

The exhaust gasses are directed through EGR system cooler to
remove heat before gasses arrive at EGR valve. Engine coolant is used to reduce
exhaust gas temperature by directing coolant flow through the EGR system

EP Sensor:

The EP sensor is a variable capacitor sensor that is
supplied a 5-volt reference signal by PCM and returns a linear analog voltage
the signal that indicates pressure. The EP sensor measures pressure in the LH
exhaust manifold. The sensor feedback signal is used for VGT and EGR valve

6.4 L Diesel Engine:

Exhaust Gas Recirculation (EGR) Oxidation Catalytic
Converter (OC)

The EGR OC, Fig. 48, helps keep EGR coolers clean by
removing deposits and exhaust condensation and preventing corrosion in
downstream components.

Fig. 48 Exhaust Gas Recirculation (EGR) Oxidation Catalytic Converter (OC). Ford 6.4L diesel engine:




Exhaust Gas Re-circulation (EGR) Coolers:

The exhaust gasses are directed through two EGR coolers,
Fig. 49, to remove heat before gasses arrive at EGR valve. Engine coolant is
used to reduce exhaust gas temperature by directing coolant flow through EGR






Fig. 49 Exhaust Gas Recirculation (EGR) coolers. Ford 6.4 L
diesel engine:


Exhaust Gas Recirculation Temperature (EGRT) Sensor:

The EGRT sensor is a thermistor device that monitors exhaust
gas temperature before EGR coolers. The electrical resistance of a thermistor
decreases as temperature increases and increases as the temperature decreases.
The varying, non-linear resistance affects voltage drop across sensor terminals
and provides an electrical signal to PCM that corresponds to measured
temperature. The EGRT sensor is used to determine whether EGR coolers are
operating correctly.

Exhaust Gas Re-circulation Temperature 2 (EGRT2) Sensor:

The EGRT2 sensor is a thermistor device that monitors
exhaust gas temperature after EGR coolers. The electrical resistance of a
thermistor decreases as temperature increases and increases as the temperature
decreases. The varying, non-linear resistance affects voltage drop across
sensor terminals and provides an electrical signal to PCM that corresponds to
measured temperature. The EGRT2 sensor is used to determine whether EGR coolers
are operating correctly.

Exhaust Gas Re-circulation (EGR) Valve:

The EGR valve is a variable position valve that controls the
amount of exhaust that enters the intake manifold. The PCM controls the EGR
valve, which operates between -100 and 100% duty cycles, which cannot be viewed
by a scan tool.

Exhaust Gas Re-circulation (EGR) Valve Position Sensor:

The EGR valve position sensor is a potentiometer sensor that
monitors EGR valve movement. The valve position signal is monitored for the
desired EGR valve travel position. The sensor is integral to EGR valve.

6.7 L Diesel Engine:

EGR Cooler:

The EGR cooler, Fig. 50, removes heat from exhaust gases
before gases enter the intake manifold. The EGR cooler is located above RH
valve cover. When exhaust gases are directed through EGR cooler, coolant from
the secondary cooling system reduces exhaust gas temperature. The exhaust gases
are directed through EGR cooler by a Powertrain control module (PCM) controlled EGR cooler bypass valve.

Fig. 50 EGR cooler. Ford 6.7 L diesel engine:

EGR Cooler Bypass Valve:

The exhaust gases are directed through an EGR cooler by EGR
cooler bypass valve, Fig. 51, to remove heat before entering the intake manifold.
The EGR cooler bypass valve is internal to EGR cooler and mounted to RH valve
cover, below EGR valve. When EGR cooler bypass valve solenoid is commanded to
0% duty cycle by PCM, EGR cooler bypass valve is closed. When EGR cooler bypass
valve is closed, exhaust gases pass through EGR cooler to the intake manifold.
When EGR cooler bypass valve solenoid is commanded to 100% duty cycle by PCM,
EGR cooler bypass valve is opened. When the EGR cooler bypass valve is open,
exhaust gases pass directly to the intake manifold without passing through EGR

Fig. 51 EGR cooler bypass valve. Ford 6.7 L diesel engine:


EGR Cooler Bypass Valve Solenoid:

The EGR cooler bypass valve solenoid is a PCM controlled
vacuum solenoid. The EGR cooler bypass valve solenoid controls EGR cooler
bypass valve position by applying vacuum from the vacuum pump to EGR cooler
bypass valve actuator. The EGR cooler bypass valve solenoid is located at the
top front of EGR cooler. When the EGR cooler bypass valve solenoid is commanded
to 0% duty cycle by powertrain control module (PCM), no vacuum from the vacuum
the pump is applied to EGR cooler bypass valve actuator and EGR cooler bypass valve
is closed. When the EGR cooler bypass valve is closed, exhaust gases pass through
EGR cooler to the intake manifold. When EGR cooler bypass valve solenoid is
commanded to 100% duty cycle by PCM, vacuum from the vacuum pump is applied to
EGR cooler bypass valve actuator and the EGR cooler bypass valve is opened.
When the EGR cooler bypass valve is open, exhaust gases pass directly to the
intake manifold without passing through EGR.

Exhaust Gas Recirculation Temperature (EGRT) Sensor:

The EGRT sensor is a thermistor type sensor. The EGRT sensor
is an input to PCM and monitors the exhaust gas temperature after EGR cooler.
The electrical resistance of the sensor increases as temperature decreases and
resistance decreases as temperature increases. The varying resistance changes
voltage drop across sensor terminals and provides electrical voltage to PCM
corresponding to the temperature. The EGRT sensor is used to determine if EGR
cooler is operating properly.

EGR Valve:

The EGR valve is a variable position valve that controls the
amount of exhaust that enters the intake manifold. The PCM controls EGR valve,
which operates between 0 and 100% duty cycles. The EGR valve operation can be
Monitored by viewing EGRVP PID, which displays the EGR valve position. The EGR valve position sensor is an integral EGR valve.

Inspect the system for proper installation of the EGR valve,
control switches, and sensors. Inspect for proper connection of electrical
connectors and mechanical linkage.

Selective Catalytic Reduction (SCR) System:

6.7 L Diesel Engine:

The SCR catalyst, Fig. 52, reduces NOx present in the
exhaust stream to nitrogen (N2) and water (H2O). At the inlet of SCR catalyst
is a port for reductant injector, followed by a louvered diffuser and a twist
mixer. DEF (Diesel Exhaust Fluid) is a solution of urea in deionized water.
When DEF is introduced into the system, it finely atomizes in the louvered diffuser and mixes evenly with exhaust gases in the twist mixer. During this time, the heat of exhaust gases causes urea to split into carbon dioxide (CO2) and ammonia (NH3). As the ammonia and NOx pass over the SCR catalyst, a reduction reaction takes place, and ammonia and NOx are converted to N2 and H2O. This reaction takes place at up to 95% efficiency and allows the engine to run leaner and more efficiently, since the high NOx levels that are produced under lean conditions
are eliminated.

Fig. 52 SCR catalyst. Ford 6.7 L diesel engine:





The SCR system should be inspected for damaged and missing
components. The instrument panel DEF indicator should be checked to ensure the
DEF tank is sufficiently filed. If the vehicle does not have DEF indicator,
check the tank fluid level.










The turbocharger increases engine power by pumping
compressed air into the combustion chambers, allowing a greater quantity of
fuel to combust at the optimal air/fuel ratio. The turbine spins as exhaust gas
flows out of the engine and over turbine blades and turns the compressor wheel
at other ends of the turbine shaft, pumping more air into the intake system.


Engine Stalling Problems

A Stalling problem most of the time is the inadequate of fuel and/or too much air. A cold engine needs a rich mixture to start and run cold, and to idle. Any of the following can cause or contribute to a hard start and/or stalling problem:

Possible problems which might affect these conditions are:

Note: Do the basics first. Visual checks such as checking the air filter and perform a fuel pump pressure test. And checking all vacuum line connections.

A vacuum leak from gaskets and/or vacuum hoses. Check for loose or broken vacuum hoses, leaks around the intake manifold gasket or throttle body, leaks around the PCV valve and EGR valve, and around brake booster.

A dirty or defective airflow (Mass Air Flow) sensor. Mass air flow sensor that has been contaminated by fuel varnish or dirt will under-report airflow and be slow to react to changes in airflow. This can upset the air/fuel mixture causing idle, stalling and hesitation problems. Cleaning the airflow sensor wire with aerosol electronics cleaner can often restore normal operation and cure the problem.

A coolant temperature sensor could be out of range. Computer needs in input from the (CTS) coolant temp sensor signal for (ECM) Electronic Control Module to effectively supply the correct amount of fuel to injectors. Take a scanner which can which can read the Live data and verify the temperature reading of sensor compared to engine temp. If reading, lets say, is 198 degrees and the engine is cold, say, 50 degrees, then you know the temp sensor is inaccurate. Replace the temp sensor.

Note: Even though you do not have any codes does not mean one of the sensors is out of range. A code simply means you have an electrical problem with either a wire to sensor connector or a bad sensor.

A defective idle speed control system. Idle speed on a fuel injected engine is controlled by allowing a small amount of air to bypass the throttle. If the idle air bypass circuit is plugged with dirt or fuel varnish or the solenoid valve is sticking or broken, the engine may not get enough air to idle normally causing it to stall. Cleaning the idle air bypass circuit in the throttle body with aerosol throttle cleaner will often remove the gunk and solve your stalling problem. If a good soaking with cleaner fails to fix the stalling problem, check the wiring connector. It might be loose or corroded. If no wiring faults are found, you may have to replace the idle speed control solenoid.

A bad Manifold Absolute Pressure (MAP) sensor. This sensor monitors intake vacuum, which the PCM uses to determine engine load. If the MAP sensor is not reading accurately, the PCM may add too much fuel or not enough, causing the engine to stall. See the article on MAP sensors for how to diagnose this sensor.

Low engine compression. If your engine has a lot of miles on it and compression is low because the piston rings and/or cylinders are worn out it has one or more leaky valves, it may not have enough oomph to keep idling. A compression check will tell you if this is a problem or not, and if it is there is no easy fix other than to overhaul or replace the engine.

Worn or fouled spark plugs. Ignition misfire can make any engine stall at idle. When the engine is running slowly, there is less momentum to keep it going, so a bad misfire may cause it to stall if the spark plugs have not been changed in a long time, a new set of plugs and/or plug wires can restore a good hot spark and eliminate the misfire. A weak ignition coil or a faulty crankshaft position sensor may also cause a stalling problem.

Bad Gas. Gasoline that contains too much alcohol (more than 10%). or gasoline that has been contaminated with water or some other substance may not burn well and cause your engine to stall. If the stalling started to occur shortly after you’re the last fill-up, suspect bad gas. The cure is to drain the tank and refill it with fresh gas from another filling station, or add some isopropyl to gas and just use up the bad fuel (if the engine runs okay at highway speeds), then refill at another station when the tank is near empty.

Problem: Your engine stalls when you stop for a traffic light or when idling:

A stop light or idle stall often means the engine is not idling fast enough (idle speed too low), or the engine is being pulled down by a load on it created by the air conditioning compressor and/or alternator- it could also mean the fuel mixture is too rich or too lean, causing the engine to run poorly, or a bad or clogged Exhausts Gas Recirculation (EGR).

Possible causes that may contribute to this kind of stalling include:

Exhaust Gas Recirculation. This part known as EGR for short is a well know problem. When coming to a stop, the egr hangs open, due to carbon deposits or clogged ports or tube. This part will cause vacuum leaks as well, so check the EGR first.

A Bad A/C compressor. If the compressor is binding up, possibly due to a lack of lubrication, internal wear or an over-charged system (too much refrigerant), it may be lugging down the engine when it is engaged. If the problem only occurs when the NC is on, there is an issue with the air-conditioning compressor.

Unusually high electrical load on the charging system. If the battery is run down and the alternator is working hard to recharge it, the increases load on the engine may pull down the idle rpm to the point where it causes the engine to stall. Check the battery state of charge to see if the battery is run down or failing. Alternator average should charge at a rate of 13.3 to 14.8 volts at idle. If the battery is low, use a battery charger to recharge it. If the battery is failing and is not holding a charge, time to buy a new battery.

NOTE: Using a voltmeter, while the engine is running, at idle you can test the alternator output. – Red lead of the meter to the positive and Black lead of the meter to the negative side of the battery. A reading between 13.3 to 14.8 volts is a good range for charging. Make sure all accessories are off. In addition, to Load test the battery you will need a load tester or go to your local parts store. They should be able to perform the load test for free. Remember testing the battery engine off with a voltmeter is not a true way to load test. With that said, any battery you test with a meter, dead or charged will read the batteries voltage until a load is applied. A battery is only as good as its weakest one.

Problem: Your engine just stalls unexpectedly while driving:

Stalls like this are often ignition-related and happen when the engine loses spark. The underlying cause is often a bad crankshaft position sensor, or sometimes a failing ignition coil (if the engine has only one coil). A faulty ignition switch that loses contact intermittently may also cause the engine to suddenly die for no reason.

When this happens, open the hood and check for spark. This can be done by pulling off a plug wire (if the engine has plug wires), and placing the end near the block while a helper cranks the engine. DO NOT hold the wire as it may shock you if the ignition system is working. If you do not see a spark or hear the plug wire snapping when the engine is cranking, the fault is in the ignition system.

If the engine has spark, it may have died due to a loss of fuel pressure. When fuel pumps fail, they usually just quit with little or no warning. The engine usually won’t restart and the vehicle has to be towed in for repairs. Listen for a buzz from the vicinity of the fuel tank when the ignition is turned on. No buzz means the fuel pump isn’t running. It might just be a blown fuse or a bad relay, but on a high mileage vehicle is often a bad fuel pump.

Another possibility is a bad ECM (engine computer) relay. The power supply to the PCM is often routed through one or two main power relays. If one of these relays loses contact momentarily, it’s like pulling the plug on the PCM. The ECM shuts down and turns off the ignition and fuel injectors, causing the engine to stall. One way to see if this is a possibility is to switch or replace the ECM power relay(s). If the problem goes away, the cause was a bad relay. If it continues, the fault is something else (possibly a wiring fault in the ECM relay or ECM power circuit).

Yet another possibility is low system voltage, loss of voltage, or overcharging. The PCM and other control modules require a steady 12 volts to operate correctly. If the supply voltage suddenly drops below 9 volts, or surges about 14 volts, or cuts out, the Electronic Control Module may temporarily kill the injectors or ignition circuit. The underlying cause may be an intermittent short somewhere in the electrical system or charging system that causes a momentary drop or surge in voltage. These can be very difficult to find, and often require hooking up a scan tool that can capture snapshot data when the stall occurs. By looking at the data, a technician can see the chain of events that caused the stall, and hopefully, identify, isolate, and repair the fault.

By Master Tech Lee Davidian, Sr. | 24 Hour Mobile Mechanics

About Master Tech Lee

38 Years as an Automotive Repair Technician / Mechanic
Import & Domestic Gasoline and Diesel Electronic Engine Control Diagnostic & Repair
ASE Master Certified
Member of Automotive Service Educational Program (GM ASEP)
Member of Clean Air Act Society
Member of MACS
25 Years of Management Experience
Personally Trained over 2,200 Automotive Technicians


Automotive Mechanical/Electrical Diagnostic Troubleshooting
Training Automotive Technologies to workforce entry-level and Advanced Students
Keeping the Customer Satisfaction Index (CSI) at a stellar rate
Writing Articles and Answering Questions for

Maintaining automotive maintenance

Automotive Maintenance is something most of us ignore until our vehicle stops functioning, that is. And then we wonder what went wrong, where. Auto Maintenance is one of the most serious aspects of ownership. It determines the longevity, performance, and reliability of whichever vehicle you drive.

Therefore regular maintenance is crucial. (Follow your car or truck Owner’s Manual)

Owner checks and service

When you fill up the gas tank you should check


Inspect the engine oil level and add the proper oil when necessary. Note: Remember most cars should burn oil every 2000 miles or more. If you never had to add oil, it means the top half of your engine is not getting proper lubrication. That would indicate an engine problem. Reason is, the upper half of your engine “Valves” needs oil to lube all the moving parts in the engine head area.

NOTICE: It is important to check your oil regularly and keep it at the proper level. Failure to keep your engine oil at the proper level can cause damage to your engine not covered by your warranty.


Inspect the engine coolant level and coolant mixture when necessary.


Inspect the fluid level in the windshield washer tank and add the proper fluid when necessary.

The following information covers the tests, inspections, and services required to maintain the safety, dependability, and emission control performance of the vehicle. Complete the necessary repairs and procedures on time. Use only the recommended fluids and lubricants.

At least once per month

Tire Inflation

Visually inspect tires including the spare tire. Verify that the tires are inflated to the pressures specified on the Certification/Tire label located on the driver door lock pillar.

Tire wear inspection and rotation every 6000 miles

Tire rotation may be required for high mileage highway drivers prior to the Engine Oil Life System service notification. Check the tires for wear and, if necessary, rotate the tires.

At least once per month

Starter switch check

CAUTION: When you are doing this inspection, the vehicle could move suddenly. If the vehicle moves, you or others could be injured

  • Ensure that you have enough room around the vehicle, which should be parked on a level surface.
  • Firmly apply both the park brake and the regular brake.
  • Start the engine:

On automatic transmission vehicles, try to start the engine in each gear. The starter should work only in PARK (P) or NEUTRAL (N). If the starter works in any other position, the vehicle needs service.

On manual transmission vehicles, put the shift lever in NEUTRAL (N), push the clutch down halfway and try to start the engine. The starter should work only when the clutch is pushed down all the way to the floor. If the starter works when the clutch is not pushed all the way down, the vehicle needs service.

Automatic transmission shut lock control check

CAUTION: When you are doing this inspection, the vehicle could move suddenly. If the vehicle moves, you or others could be injured. Personal injury or property damage may result. Make sure there is enough room around the vehicle, in case the vehicle does move. Do not use the accelerator pedal, and be ready to turn OF1 the engine immediately if it starts. 

  • Ensure that you have enough room around the vehicle, which should be parked on a level surface.
  • Firmly apply the parking brake. Be ready to apply the regular brake immediately if the vehicle begins to move.
  • With the engine off, turn the key to the RUN position, but do not start the engine.
  • Without applying the regular brake, try to move the shift lever out of PARK (P) with normal effort.
  • If the shift lever moves out of PARK (P), the vehicle needs service.

Ignition transmission lock check

  • With the vehicle parked, set the parking brake.
  • Try to turn the ignition key to LOCK in each shift lever position:
  • With an automatic transmission, the key should turn to LOCK only when the shift lever is in PARK (P).
  • With a manual transmission, the key should turn to LOCK only when you press the key release button.
  • On all vehicles, the key should come out only in LOCK.

Park brake and automatic transmission park (p) Mechanism Check

CAUTION: When you are doing this inspection, the vehicle could move suddenly. If the vehicle moves, you or others could be injured. 

CAUTION: When performing this check, the vehicle could move suddenly. Personal injury or property damage may result. Make sure there is enough room around the vehicle, in case the vehicle does move. Do not use the accelerator pedal, and be ready to turn OFF the engine immediately if it starts. You or others could be injured, and property could be damaged. Make sure there is room in front of your vehicle in case it begins to roll. Be ready to apply the regular brake at once should the vehicle begin to move. 

Follow this procedure to test the parking brake and an automatic transmission PARK mechanism:

  • Park on a fairly steep hill, with the vehicle facing downhill.
  • Keep your foot on the hydraulic brake pedal.
  • With the parking brake set, perform the following test:
  • Start the engine.
  • Place the transmission in NEUTRAL.
  • Slowly remove foot pressure from the regular brake pedal. If the vehicle moves adjust Park Brake. In order to check the PARK (P) mechanism of an automatic transmission, additionally perform the following test:
  • Release all brakes. If the vehicle moves adjust Park Brake.

Under body flushing service

Every spring uses  plain water to flush any corrosive materials from the underbody. Clean any areas where mud and another debris can collect thoroughly. And also, go to the nearest car wash and high-pressure spray engine with soap and rinse. All the above will keep oil and debris from softening hoses and corroding electrical components. Especially cars in colder climates, due to the salt trucks spreading the roads, can do a lot of damage to electrical components in the engine bay, anti-lock wheel sensors, and ride controls.

Positive Crankcase Understanding

History of the PCV – Positive Crankcase Ventilation valve:

Before the 1960s car engines were vented to the atmosphere. That is, toxic vapors that were created by exhaust gasses leaking past the rings (called “blow-by”) and into the crankcase were simply allowed to flow out of the engine. PVC was, usually, accomplished by a metal tube that routed from the top of the engine down underneath. The air flowing under the car helped to draw vapors out. As engines aged, those vapors contained more and more soot and other contaminants that contributed to smog and overall pollution.

GM researchers identified engine blow-by gas as a primary source of hydrocarbon emissions and developed the Positive Crankcase Ventilation valve, commonly known as the PCV valve, to cap the leak. Made standard on all GM cars sold in the U.S. beginning in 1963, it was the industry’s first vehicle emissions control device. Before 1963, the PCV was only used in California. There is a variety of PCV systems used on various makes and models of cars produced since 1963, but all function essentially the same.


PCV-control-valve-actionPCV control valve action:

Vapor is then carried with the fuel/air mixture into the combustion chambers where it is burned. Since the manifold vacuum is constantly changing, some control must be in the system. This control device is the Flow Control Valve, commonly referred to as the PCV Valve.

PCV systems can be described as either open or closed. The two systems are quite similar. However, the closed system in use since 1968 is more effective at air pollution control. The systems differ in the manner in which fresh air enters the crankcase, and excessive vapor is expelled.

Positive Crank Case Understanding:

Open PCV Systems:

The open system draws fresh air through a vented oil filler cap; usually, chrome plated in restored cars. This works fine as long as the vapor volume is minimal and when the engine is running. However, when the crankcase vapor becomes excessive – or when the engine is shut off – it is forced back through the vented oil filler cap and into the open atmosphere. The open PCV system, though successful at removing contaminated vapors from the crankcase, is not completely effective as a pollution control device.

Closed PCV Systems:

The closed PCV system draws fresh air from the air filter housing. The oil filler cap in this system is NOT vented. Consequently, excess vapor will be carried back to the air filter housing and from there into the intake manifold. The closed system prevents vapor, whether normal or excessive, from reaching the open atmosphere. The closed system is very effective as an air pollution control device.


The PCV Valve – More Complicated Than You Think:

The purpose of the PCV valve is to meter the flow of the vapor from the crankcase to the intake manifold. This is necessary to provide proper ventilation for the crankcase while not upsetting the fuel/air mixture for combustion.

Blow-by gasses and vapor should be removed at about the same rate they enter the crankcase. Since blow-by is minimal at idle and increases during high-speed operation, the PCV valve must control the flow of vapor accordingly. The PCV valve is designed to compensate for the engine ventilation needs at varying engine speeds. It is operated by manifold vacuum, which increases or decreases as engine speeds and loads change.

For example, at low or idle engine speeds manifold vacuum is high. This pulls the plunger to the extreme forward position or manifold end of the valve. Due to the shape of the plunger, vapor flow is reduced to a minimum. The low rate of the flow is adequate for ventilation purposes and will not upset the fuel/air mixture ratio.

At high speeds, manifold vacuum is decreased. The plunger is only drawn to a point about midway in the housing. This allows a maximum flow of vapor. Since the engine needs more fuel/air mixture at high speeds, the introduction of more vapor does not significantly affect performance. In the event of a backfire, pressure from the intake manifold forces the plunger to the closed or engine-off position. This prevents the backfire flame from reaching the crankcase and exploding the combustible vapor.

Okay? Now What If It Isn’t Working Properly?

A neglected PCV system will soon fail to function, and the result can be expensive as well as troublesome for the car owner. If the crankcase is not adequately ventilated, the motor oil will become contaminated, and heavy sludge accumulations will begin to form. Internal parts, not protected by the motor oil, will start to rust and corrode due to the water and acids that will become trapped within the crankcase.

If the PCV system is not functioning properly, the flow of crankcase vapor into the intake manifold will not be correctly metered. This, in turn, will upset the fuel/air mixture for combustion and can cause rough idling or even stalling of the engine. Furthermore, intake and exhaust valves, in addition to sparking plugs, may eventually be burned and rendered useless, prematurely affecting performance and requiring expensive repairs. To assure trouble-free performance of the PCV system and, in turn, the engine and vehicle, routine maintenance of the PCV system are recommended and required.

Myth Time!

Millions of owners think that if a PCV valve rattles when shaken that it is okay. Wrong! Just because it rattles doesn’t mean its calibrated spring is metering correctly. Cleaning the PCV doesn’t accomplish anything either. A PCV valve should never be cleaned and placed back into service. Cleaning the PCV valve will result in a clean PCV valve; not a new PCV valve.

Some contaminants will remain in the PCV valve that can never be flushed out. Additionally, there is an amount of wear that will be experienced by the spring that cleaning cannot replace.


What are the Symptoms of a Bad PCV VALVE?

The positive crankcase ventilation or PCV valve is an inexpensive and the part most consumers overlook. It is also one of the possible causes of expensive oil leaks and sludge buildup inside the engine.

All automotive engines are lubricated with oil, and when oil is churned by moving parts, pressure is produced by combustion. Piston rings and valve guides also leak slightly producing pressure, called Blow-by,  in the crankcase. Many years ago, the engines would simply vent the pressure into the atmosphere with a road-draft tube and breather cap. Today we use a positive crankcase ventilation or PCV system to handle this, and also to help lower the harmful emissions engines produce.

The most common problem that afflicts the PCV systems is a plugged up PCV valve or hose. Accumulation of fuel and oil varnish deposits and sludge inside the valve can restrict or even block the flow of vapors through the valve. A restricted or plugged PCV valve cannot pull moisture and blow-by vapors out of the crankcase. The valve can cause engine-damaging sludge to form and the backup of pressure that may force oil to leak past gaskets and seals. The loss of airflow through the valve can also cause the air/fuel mixture to run richer than normal, increasing fuel consumption and emissions. The same thing can happen if the pintle inside the PCV valve sticks shut.

If the pintle inside the PCV valve sticks open or the spring breaks, the PCV valve may flow too much air and lean out the idle mixture. The PCV may cause a rough idle, hard starting and lean misfire (which increases emissions and wastes fuel). The same thing can happen if the hose that connects the valve to the throttle body, carburetor or intake manifold pulls loose, cracks or leaks. A loose or leaky hose allows “unmetered” air to enter the engine and upset the fuel mixture, especially at idle where the idle mixture is most sensitive to vacuum leaks.

On late model vehicles with computer engine controls, the engine management system will detect any changes in the air/fuel mixture and compensate by increasing or decreasing short term and long term fuel trim (STFT and LTFT). Small corrections cause no problems, but large corrections (more than 10 to 15 points negative or positive) will typically set a lean or rich DTC and turn on the MIL.

Problems can also occur if someone installs the wrong PCV valve for the application. The flow rate of the PCV valve is calibrated for a specific engine application. Two valves that appear to be identical on the outside (same diameter and hose fittings) may have different pintle valves and springs inside, giving them very different flow rates. A PCV valve that flows too much air will lean the air/fuel mixture while one that flows too little will richen the mixture and increase the risk of sludge buildup in the crankcase.

Watch out for cheap replacement PCV valves. They may not flow the same as the OEM PCV valve. Quality OEM brand replacement PCV valves are calibrated to the specs the manufacturers designed them to operate in, which provide long-lasting, trouble-free performance.

Note: On many 2002 and newer vehicles with OBD II. the OBD II system monitors the PCV system and checks the flow rate once during each drive cycle. But on older OBD II and OBD I systems, the PCV system is NOT monitored. So the problem with the PCV system on a pre-2002 vehicle probably won’t turn on the MIL (malfunction indicator lamp) or set a diagnostic trouble code (DTC). 


How the PCV system works:

The PCV system is relatively straightforward. An inlet hose connects to a filtered air source. This is used to supply clean air that is drawn through of the engine. Most of the time this air is supplied through the engine air filter. On a few designs, there is a separate inlet filter that cleans the incoming air for the PCV system only. This filtered air flows through the engine, picking up fumes and vapors. The air exits through another hose, connected to manifold vacuum. The flow of air draws fumes from the crankcase and burns them harmlessly in the engine. This also creates a slight vacuum, relieving any pressure that may build. Negative pressure helps to prevent oil leaks and oil consumption by the engine. The PCV valve also helps regulate the amount of airflow, which helps prevent oil being drawn out of the engine.

The PCV Valve system helps remove moisture, a major contaminant, from the oil:

Note: PCV system helps remove moisture from oil if driven far enough.

When the engine is running, it generates a large amount of heat and as the engine cools, condensation forms inside the engine. Engine oil additives help absorb this moisture and keep it in suspension. If the moisture content exceeds the capacity of the additives, it will start to attack the metal parts of the engine causing internal engine damage. Keeping up with your regular Oil Changes will help reduce moisture.




Moisture contamination in the PCV system:PCV-system-helps-remove-moisture (1)

A sign of engine moisture contamination will show a cloudy or milky film in the PCV valve or hose. If you find water in the PCV valve system, and its hoses, suggests a need for replacement but is also an indication of other problems. Replacing the PCV valve will help get rid of some problems, but the main issue remains, and symptoms will soon return. If we only drive a vehicle on short trips, moisture content means we need more frequent oil changes and longer drive cycles. A moisture buildup with normal driving shows other engine problems, such as Head Gasket, or Cracks, or Intake Manifold Gasket problems. Several areas of the engine can allow leakage and oil contamination. Engine Seals and Valve Cover gaskets are the most common areas to leak first. Coolant leaking into the oil is a very serious problem. Without immediate correction, engine damage is likely to occur.

Note: the milky film seen in the PCV Valve system is due to a chemical reaction from the anti-freeze. If no anti-freeze is present in the cooling system, you will not see the whiteness. You have seen oil spills in the ocean from the news, and the oil is still black in color floating on the ocean top, correct?

The engine’s oil filter helps to remove the contaminants from the oil, which are by-products of combustion and moisture. It’s these things that cause internal engine problems over time if the oil and filter are not changed on a regular basis. This is one reason oil changes are a must. Short trips make the problem far worse as the engine does not reach full temperature. Oil and filter should be replaced more often when the average driving distance is under ten miles. As the engine reaches full temperature, after about 20 minutes of driving, the heat of the oil causes the moisture to boil off and out through the suction action of the PCV Valve. If the vehicle is driven far enough, the PCV system will pull much of this moisture from the oil, in the form of steam. This is one reason vehicles can go further between oil changes when the average trip is very long. With short trips, this does not occur, requiring more frequent oil changes. The type of driving determines oil change needs and is a better guide than just the number of miles driven.

Read – Preventive Maintenance Goes a Long Way 

 If the PCV system fails, severe sludge buildup and oil leaks can occur.A plugged PVC valve allows moisture buildup resulting in sludge:



A plugged PCV valve causes many other engine problems. Pressure begins to build, and gaskets and oil seals may fail. When an engine suffers multiple oil leaks, You should always inspect the PCV system. Another problem is a lack of air flow to carry vapors from the crankcase. Without air flow, moisture contamination remains, and a sludge buildup is often the result. Operating the engine without adequate ventilation is a leading cause of engine sludge.


How a PCV valve works:

Most engines employ a PCV valve at the point where fumes are drawn out of the engine. The PCV valve serves several functions. At an idle, engine vacuum is very high, around 16 to 20 inches (Hg). This high vacuum would tend to draw oil, as well as fumes from the engine. The PCV valve acts as a buffer against oil being drawn out. It also regulates the amount of vacuum applied to the engine, based on the engine’s load and speed.The operation of PCV valve under different conditions:

The operation of PCV valve under different conditions:


At an idle, engine speed is low, around 600 RPM. A relatively small amount of fuel and air travel through the intake at idle speed. If the PCV valve does not regulate air flow, the engine will act like it had a vacuum leak. Too much air flowing into the intake causes the engine to lean out (too much air in relation to the fuel) and misfire. At an idle, the PCV valve restricts air flow, to reduce this problem. At high manifold vacuum (idle), spring loaded valve is drawn up and partially restricts flow to the crankcase. The first drawing above illustrates the PCV valve position at idle.

On engine acceleration, more fuel and air move through the engine and intake manifold and the vacuum is much lower. Air introduced by the PCV valve has a less of an effect on the fuel-air mixture. Low intake manifold vacuum allows the valve to move to a more central position. In this position, the system draws more combustion vapors from the crankcase. The additional flow is very beneficial, without affecting engine performance. The center illustration above shows the PCV valve in the acceleration mode position.

Any pressure in the intake causes flow in the opposite direction. The action of the PCV valve to the pressure will occur during an engine backfire, engine miss, or if the engine is turbocharged. The PCV valve can act as a check-valve in these situations. By the PCV valve closing, any positive pressure, the fuel vapor is prevented from entering the crankcase. Even if a minuscule amount of positive pressure can force oil through gaskets and seals and cause oil and vacuum leaks. Failure of the valve to seal positive pressure may damage the engine.

PCV valve grommets and hoses:

Many problems in the PCV Valve system originate from the hoses and mounting components, rather than the valve itself. A PCV valve attaches to the engine in many ways, depending on the design. Manufacturers often use rubber grommets, inserted into a hole in the valve cover. The pliable rubber grommet seals the valve to the cover and holds it in place. On other designs, the valve may screw in or twist-in and seal with on O-ring. The PCV valve must be completely sealed for maximum benefit, very important! Any leak will cause problems, so always inspect the positive crankcase system closely.


Replacing the PCV grommet with the valve prevents problems:

Rubber grommets and O-ring seals get hard over time and cause problems. Grommets sometimes crack and split, creating an oil leak and allowing dirt into the engine. Replacing the grommet or O-ring with the valve prevents many problems. Grommets come in a variety of designs, depending on the engine design. Original equipment manufacturer (OEM) grommets work and fit best. If the PCV valve mounts with a grommet, purchase a new one with the valve.

PCV inlet and outlet hoses are also prone to deterioration. Check all hoses in the system when replacing the valve. Hose(s) may become oil soaked and swell, preventing them from sealing the engine. Many hoses get hard with age and crack. A leaking PCV inlet or outlet hose can cause a check engine light or allow debris into the engine.

Automotive manufacturers design the hoses in the PCV system for vacuum and to be oil resistant. Vacuum hose has a stiff sidewall to resist collapsing. These are very different from fuel hose or heater hose, which they design to hold pressure. Always replace the PCV Valve hoses with the original equipment molded hose, from the vehicle manufacturer. Substituting any other hose types very often leads to problems and may cause the positive crankcase ventilation system to fail, creating oil leaks and allow a sludge buildup.

Collapsed PCV hose will block, or restrict the PCV Valve Vacuum flow:

Inspect-all-hoses-in-the-PCV-systemEven original equipment hoses sometimes give problems. This is common on Ford and some Mazda vehicles. The hose chosen is not adequate for the task, and after miles of use, it will collapse.
When this occurs, flow to PCV valve system stops, and the hole in the supply hose may create a vacuum leak. Inspect all hoses in the PCV system and replace any that appear soft, swollen or collapsed.





Failure and testing of the PCV valve:

As the PCV valve ages, several things may happen. Gunk and sludge can cause the valve to stick in the open position. Eventually, will produce an engine vacuum leak and might result in a misfire at idle. Too much air flow causes the engine to lean out, possibly setting a check engine light. The excess flow could also draw oil from the engine, causing oil consumption.

The rattle test gives an indication but is not conclusive:



Because PCV valves fail in different ways, no test will show all the possible problems. For instance, the old test of shaking the valve and listening for a rattle is only partially helpful. No rattle may show a stuck valve, on many designs, but the valve could rattle freely and still be bad. Use Best Practices and change the valve. This little cheap part, if not changed in time, will cost thousands of dollars in engine repairs if not changed at the recommended interval.


Fresh oil in the PCV hose suggests a problem:




Another definitive PCV valve test is to remove the vacuum hose and look for fresh oil. A PCV vacuum hose, with oil dripping or a wet valve, usually suggest too much flow, which causes oil consumption. Checking the PCV vacuum hose is a wise precaution, on any engine that consumes oil. Also, if you see blue smoke coming from the tailpipe can mean many reasons, but the first step is to check the PCV valve. Basics First!


EGR back pressure manometer


The digital manometer can detect a plugged PCV valve:

The PCV valve flows at different rates, under various driving conditions. For instance, at high engine vacuum, the valve should hardly flow at all. An Excess flow at an engine idle will interfere with smooth running. With a lower intake vacuum, flow through the PCV valve increases. A quality auto repair shop will have a tool called a manometer. The manometer measures the very small negative pressure in related to flow. Testing is done at the engine idle speed, under acceleration, and under a positive intake condition.

A PCV valve can also stick in the closed position, which allows crankcase pressure and blow-by to build up the pressure and can damage gaskets and seals. Auto Technicians also test back pressure with a manometer. Positive pressure in the crankcase is a sign of a problem. When the engine begins to develop oil leaks, especially at multiple locations, the PCV system should always be considered.

Extensive testing may be a moot point as the cost of a replacement valve is normally very low. Cleaning an old valve is much the same. It is rarely effective, and replacement of any suspected PCV valve is often far more practical.

PCV valve design variations:Heating-Coil-Inside-the-PCV-Valve

For many years, the PCV valve remained relatively unchanged. Today a multitude of designs and sizes exist, but most operate in a similar manner. A few manufacturers add heating elements to their PCV valves. It is thought cold temperature could cause a non-heated valve to freeze and stick, because of moisture is drawn through the system. By heating, keeps the PCV valve from freezing is prevented.


Ford uses two designs for heated PCV valves as well as conventional non-heated valves on their engines. One heated design flows engine coolant through tubes to keep the valve warm. Another design is electrically operated. A heating coil inside the valve is used to keep the PCV valve from freezing.

The drawback with heated PCV valves is cost. Heated PCV valves cost many times more than non-heated valves. Most manufacturers simply rely on the engine, and crankcase vapors, heat to get the job done.

Replacing a PCV valve:

Replacing a PCV valve is normally very easy to do, once the location is found. Most simply push into a rubber grommet. Remove the exit hose and a slight twist breaks them free. A light pull removes the valve so that they can be replaced. Some Ford valves use a quarter-turn system. These are rotated a quarter turn, counter-clockwise before pulling out. A few other designs are threaded in and must be unscrewed to remove.

Read  More about PVC Valve Understanding and Testing

Click Here and Ask Us Where your PCV Valve is today


Ford Explorer with 4.0L engine, Positive Crank Case Valve Location:

Some PCV valves are also very difficult to access, and others not. Take, for instance, the 4.0L Ford Explorer, in the picture above, has a valve in the rear of the driver’s side valve cover. While it can be difficult to find the PCV valve, especially if we do not know the location, you can ask an automotive technician here on to know where your positive crankcase valve is.  To access the valve on a 2.3L Ford Escape, we remove the intake manifold. Late model Toyota four-cylinder engines may also place the PCV valve under the intake manifold. With such vast designs, replacing the valve when we remove the intake manifold for any reason is wise.

Not all engines today use the PCV valve:

Some manufacturers lower the cost of material by substituting a restrictor for the PCV valve. This PCV valve uses an orifice and a small reservoir to perform some of the functions previously handled by the PCV valve. A small hole allows enough vacuum to draw fumes from the engine, but not enough to cause a rough idle. The orifice may become clogged over time and need replacement. Hoses on such a system are also prone to deterioration and have to be replaced when they fail.

A PCV valve often lasts around 80,000 miles or more and is usually replaced at the first general ignition tune-up. Some can fail much earlier. Short [under ten miles] trips in the vehicle, will cause the valve to fail sooner. Under extreme conditions, a 30,000-mile replacement may be needed. Because of the low cost and easy to replace on most vehicles, changing the PCV valve is a wise decision. If your engine is approaching these mileages or has developed an oil leak, have the PCV system checked as soon as possible. It could save a lot of money in the long run. After all, your vehicle is your second best investment.


Modified and Additional information by Master Tech Lee

If you need help replacing your PCV valve, please contact us, and we will provide you with the replacement interval and help you step by step for free.

When you least expect it, your car, truck, semi-tractor trailer, RV, motor-home, or coach won’t start, and you need a jump start service. Even if you have jumper cables, you aren’t always able to find someone to help you out; it takes two.

When you call 24 Hour Mobile Mechanics, we will give you a low flat rate for a jump start. We will quickly dispatch an ASE Certified mobile mechanic who will first test the battery to ensure it has at least a 75% charge, then will do a load test which should be no lower than 9.1 volts. If the battery has 75% or better, he or she will jump start your car or replace your battery if a load test is below 9.1 volts. Even if further diagnosis is required, 24 Hour Mobile Mechanics have the computer diagnostic equipment and the experience to solve the issue and get you back on the road asap. You can rest easy knowing a qualified mobile mechanic is on the way whether you need a jump start service or battery replaced. Payment is made easy. We accept all major credit/debit cards, Fleet One, EFS, T-Chek, Comdata Comcheks and of course Cash. 24 Hour Mobile Mechanics is here to help when you need it the most and will get you back on the road quickly.

Load Testing a Battery - jump start serviceRemember, your battery is only there to start your vehicle. The alternator charges your battery and powers the electrical system while your car is running.

How to Eliminate Odors Coming From AC Vents


Bulletin No.: 99-01-39-004D

Date: August 10, 2011

Subject: Air Conditioning Odors Coming From Vents (Install Evaporator Core Dryer Kit and Apply Cooling Coil Coating)

Reference Number(s): 99-01-39-004D: Date of Issue: August 10: 2011

Affected Model(s): 2012 and Prior GM Passenger Cars and Trucks: All Equipped with Air Conditioning

Supersedes: This bulletin is being revised to add the 2011 and 2012 model years. Please discard Corporate Bulletin Number 99-01-39-004C (Section 01 – HVAC).

Superseded Bulletin (s): 99-01-39-004C: Date of Issue: June 12: 2009


Some customers may comment about musty odors emitted from the Heating, Ventilation and Air Conditioning (HVAC) system at vehicle start-up in hot: humid conditions.

This condition may be caused by condensate build-up on the evaporator core: which does not evaporate by itself in high humidity conditions. The odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on: the microbial growth may release an unpleasant musty odor into the passenger compartment.

There are several other possible sources of a musty odor in a vehicle. A common source is a water leak into the interior of the vehicle or foreign material in the HVAC air distribution system. Follow’ the procedures in SI for identifying and correcting water leaks and air inlet The procedure contained in this bulletin is only applicable if the odor source has been determined to be microbial growth on the evaporator core inside the HVAC module.


Many vehicles currently incorporate an afterblow function within the HVAC control module software. The afterblow feature, when enabled, employs the HVAC blower fan to dry the evaporator after vehicle shut down and this function will inhibit microbial growth. Technicians are to confirm that the customer concern is evaporator core odor and that the vehicle has the embedded afterblow feature, as defined in the SI document for that specific vehicle model, model year and specific HVAC option. Refer to SI for enabling the afterblow function. Vehicles being delivered in areas prone to high humidity conditions may benefit from having the afterblow enabled calibration installed prior to any customer comment.

IMPORTANT: If the vehicle is not factory equipped with the embedded after blow enables the feature, it may be added with the Electronic Evaporator Dryer Module Kit (P/N 12497910 or AC Delco 15-5876).

IMPORTANT: When installing the Electronic Evaporator Dryer Module, you MUST use the included electrical splice connectors to ensure a proper splice. Complete detailed installation instructions and self-testing procedures are supplied with the kit. If necessary, the Electronic Evaporator Dryer Module may be installed underhood if it is protected from extreme heat and water splash areas.

To immediately remove the evaporator core odor on all suspect vehicles, it is necessary to eliminate the microbial growth and prevent its re-occurrence. To accomplish this, perform the following procedure:

Vehicle and Applicator Tool Preparation:

  1. The evaporator core must be dry. This may be accomplished by disabling the compressor and running the blower fan on the recirculating heat setting for an extended period of time.

NOTE: Compressor engagement will cause the evaporator core to remain wet and will prevent full adherence of the Cooling Coil Coating to the evaporator core surfaces.

  1. Verify that the air conditioning drain hose is not clogged and place a drain pan beneath the vehicle.
  2. Place a protective cover over the carpet below the evaporator core.
  3. Remove the cabin air filter if equipped, and cover the opening prior to applying the Cooling Coil Coating, as the product may clog the filter. If the cabin air filter appears to have little or no remaining life, suggest a replacement to your customer.
  4. If the HVAC module has a blower motor cooling tube, be careful NOT TO SPRAY THE COOLING COIL COATING INTO THE BLOWER MOTOR COOLING TUBE
  5. Attach the Flexible Applicator Pressure Spray Tool (J-43810-20A) to a compressed air line operating at 586 kPa (85 psi) to 793 kPa (115 psi).
  6. Shake the bottle of Cooling Coil Coating well. Screw the bottle onto the cap on the applicator tool’s pick-up tube.

NOTE: The pick-up tube is designed for 120 ml (4 oz.) and 240 ml (8 oz.) bottles and should coil slightly in the bottom of a 120 ml (4 oz.) bottle.

  1. Use one of the following three methods to apply the Cooling Coil Coating.

IMPORTANT: If the Pressure Applicator Spray Tool (J-43810-20A) is not available, the Cooling Coil Coating is also available in an aerosol can (P/N 12377951 (in Canada, 10953503)).

Application Through Blower Motor Control Module Opening:

  • Remove the blower motor control module (blower motor resistor). Refer to the applicable procedure in SI.
  • Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface.
  • Apply the Cooling Coil Coating directly to the evaporator core through the blower motor control module (blower motor resistor) opening.
  • Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces.
  • When the application is complete, install the blower motor control module (blower motor resistor).

Application Through Blower Motor Opening:


  • Remove the blower motor. Refer to the applicable blower motor removal procedure in SI.
  • Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface.
  • Apply the Cooling Coil Coating directly to the evaporator core through the blower motor opening.
  • Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces.
  • When the application is complete, install the blower motor.

Application Through a Hole in the HVAC Module:

  • If neither of the two previous application methods is available, it may be necessary to drill a hole in the HVAC module.
  • Locate an area of the HVAC module between the blower motor and the evaporator core. Drill a 10 mm (3/8 in) hole in the HVAC module. Use caution to keep the drill clear of the evaporator core and the blower motor fan.
  • With the air distribution vents closed and the blower motor fan speed on HIGH, insert the applicator tool into the hole and spray the Cooling Coil Coating into the airstream toward the evaporator core.
  • Use a GM approved RTV sealant to plug the hole in the HVAC module.
  • Locate an area of the HVAC module between the blower motor and the evaporator core. Drill a 10 mm (3/8 in) hole in the HVAC module. Use caution to keep the drill clear of the evaporator core and the blower motor fan.
  • With the air distribution vents closed and the blower motor fan speed on HIGH, insert the applicator tool into the hole and spray the Cooling Coil Coating into the airstream toward the evaporator core.
  • Use a GM approved RTV sealant to plug the hole in the HVAC module.
  1. After the Cooling Coil Coating application is complete, start and run the vehicle for approximately 10 minutes, with the compressor disabled, HVAC mode set to Recirculate Max, heat set to full warm, blower motor fan speed on high, and one window’ open approximately 12 mm (1/2 in). This cures the Cooling Coil Coating onto the evaporator core surface.
  2. While the engine is running, rinse the applicator tool with warm water to prolong the life of the tool. Be sure to spray warm water through the nozzle to rinse out any residual Cooling Coil Coating still in the capillary pick up tube. Otherwise, it will dry and clog the applicator tool. Also, remove the small green valve from the bottle cap and rinse it thoroughly while rolling it between two fingers and then reinstall it. If this valve is clogged, the Cooling Coil Coating will not flow through the applicator tool.
  3. Shut off the engine and enable the compressor again.
  4. Verify proper HVAC system operation.
  5. Remove the protective cover from inside the vehicle.
  6. Remove the drain pan from underneath the vehicle.
  7. Reinstall the cabin air filter if necessary.


ACDelco-Cooling-Coil-Coating-Applicator-Kit_233x236Kit includes an Ulti-Flex Applicator tool that bends to fit any configuration and has a precision atomizing tip which assures proper cooling coil coating diffusion
Solution can be quickly applied in just 20 minutes, and the vehicle can be back on the road within an hour
Acrylic coating helps protect against unwanted odor
Part No. 10-5052

IMPORTANT: The Cooling Coil Coating listed above is the only GM-approved product for use under warranty as an evaporator core disinfectant and for the long-term control of evaporator core microbial growth.


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