egr problems

droptopford 50,

Here's an EGR system test summary that I've posted before. It's for 94/95 5-liter Mustangs specifically, but the components and principles are similar on other Ford products.

EGR SYSTEM TESTING:

First you need to see if the EGR valve vacuum diaphragm is leaking or not. You do that with the engine off. Remove the vacuum hose from the top of the EGR valve, and attach a separate 3 or 4 foot length of vacuum hose to it. Enough length to reach from the valve to you, cause unless you have a vacuum pump you’re gonna have to suck on it! (No pun intended.) Suck on the opposite end of the vacuum hose until the EGR valve opens all the way. You can see the valve moving inside the housing without removing anything from it. Then just hold the vacuum for a while and see if the valve stays put or slowly starts to close. If it stays put, you’re good! The diaphragm is not leaking.

At some point you need to make sure that the pintle (tip of the valve that closes off the flow) in the EGR valve is not all crudded up. If it is, the EGR valve will not be able to shut off the exhaust gas flow completely at idle even if it is operating correctly. That requires disassembling the EGR valve. It's not that hard actually.

If you still have EGR related trouble after you checked the vacuum diaphragm and cleaned the EGR valve, then part of the EGR control system may not be functioning properly. The other two components are the EVP (EGR Valve Position sensor) and the EVR (EGR Valve Regulator).

EVR Vacuum Test Procedure:

The EGR Valve Regulator is a vacuum regulator that the EEC computer uses to control the actual EGR valve position. It's located on the other end of the vacuum line that's connected to the EGR valve itself, which unfortunately for us 94/95 owners is INSIDE the right front fender well!!!. If the EVR is leaking (air leak) then the EEC will not be able to control EGR valve function with it, and the EVR will have to be replaced.

The good news is that if you have a vacuum gauge and an 8-foot length of vacuum hose, you don't have to take the inner fender well apart to access and test the EVR. To test it, do this: Disconnect the vacuum hose connector at the EGR valve itself. Now cut off a 1-inch piece of your 8-foot vacuum hose and push that onto the EGR valve vacuum connector. Next, push one end of a plastic “T” connector into the 1-inch piece of vacuum hose, and then reconnect the main EGR vacuum hose to the other end of the “T” connector. Use a plastic vacuum hose “T” fitting with an O.D. that matches the vacuum line I.D. (You can get a bag of various sized vacuum hose “T” connectors most auto parts stores.) So, basically, you have just spliced a “T” fitting into your EGR valve’s vacuum line so you can tap off of it. Now connect your 8-foot length of vacuum hose to the “T” connector’s “T” fitting.

Now run the vacuum hose underneath the open hood of your car, up across the windshield, and then over toward the driver's side window. Next carefully close the hood making sure the vacuum line is not pinched off by the hood. Then connect the vacuum gauge to the open end of the vacuum hose and drop the gauge into the open driver's side window of the car. So, what you have now is a vacuum gauge hanging inside the driver's side door that's directly connected to the output of your EVR, which you can monitor while you drive the car down the street. Now go for a drive! If your EVR is working properly, the vacuum gauge will read 0 (zero) inches at idle AND at wide open throttle. At any throttle position in between, the gauge should indicate some vacuum being pulled (a few to several inches or so) proportional to the throttle opening. If you get these reading, your EVR is good. If not, its bad and you'll have to take the right front inner fender well apart to replace it.

EVP Resistance Test Procedure:

If your EVR tests good, and your EGR valve is clean and visibly moving when vacuum is applied, the only other cause for an EGR related trouble code is the EVP.

The EVP (EGR Valve Position sensor) is used on most Ford engines over 4.6 liter, including the 5.0 liter. It is attached to the top of the EGR valve by screws and has an electrical connector attached to it (no vacuum connector). The EVP is a feedback device that tells the EEC computer the actual position of the EGR valve (closed, full open, part open, etc.) That completes the closed loop control of the EGR system. EEC computer controls EGR valve position via the EVR, and EVP reports EGR valve position back to the EEC computer. This loop allows continuous control of EGR valve position, with resultant modification of the A/F mixture ratio.

The things that you need to check on the EVP are that is has a good electrical connection to it (pull off the connector and make sure the three pin contacts are all clean), and that it's resistance is in spec throughout its full range of mechanical travel. If the resistance is even a little off of factory spec, it is probably bad and not sending a proper EGR valve position indication signal to the EEC computer.

EVP resistance should vary proportionally from 5,500 ohms to 100 ohms as vacuum increases from 0 to 10 inches.

To do this, make sure the ignition is not on, i.e. key off condition, and disconnect the EVP electrical connector from the EVP sensor itself. Then connect your ohm meter between the EVP pin and the VREF pin inside the connector on the EVP sensor. (There are three pins inside the connector and the connector is shaped like a "U". The VREF pin is the one at the bottom of the "U" shape, and the EVP SIG pin is the one directly opposite from the VREF pin at the top or open end of the "U".)

OK, so now we have the ohm meter leads connected to the correct two pins and set to the proper ohm scale.

Next disconnect the vacuum line to the EGR valve and connect that same three or four foot length of vacuum hose back to it that you can suck on to create a vacuum to make the EGR valve move through its entire range of travel. Of course, if you have a vacuum pump, you can use that instead of your own personal vacuum source! The EGR valve should be at max open at 10 in. Hg.

Moving the EGR valve through its entire range by applying vacuum to the EGR valve vacuum fitting causes the shaft on the EVP sensor to move through its entire range of travel also, in direct proportion to EGR opening.

Now just read the ohm meter while you are doing that and compare the resistance readings you get to the specs above. If you are off by even a little or the resistance does not vary proportionally as you apply more vacuum, the EVP sensor is probably bad.

Clearing Codes:

IMPORTANT: Remember that whenever you replace an EEC-IV system sensor (like the EVP) you MUST clear the codes from your PCM computer. If you don't, the computer will continue to use the adaptive learning settings that it was using to compensate for the bad sensor/actuator and will not start using the correct input signal from the new sensor that you just installed. Adaptive learning settings are stored in KAM (Keep Alive Memory), which is not the same as the Continuous Memory codes. Interrupting the ground latch during the KOEO test procedure only clears the Continuous Memory codes. To clear the KAM codes, you have to disconnect the negative battery cable for at least 5 minutes. Your car may act a little funky for the first 10 or 15 miles after clearing the KAM and driving for the first time. It takes about that long for the PCM computer to relearn all the sensor inputs.

Hope that helps.

MLC Stang: That is a great write up! I copied and printed it! Thanks for passing great info!
What does taking the EGR valve apart consist of? thanks

R.J. said:

What does taking the EGR valve apart consist of? thanks

Click to expand...

"Taking the EGR valve apart" is not really the correct thing to call it. What you can do is remove the EGR valve from the side of the intake elbow and take it out of the engine bay to clean the pintle and seat inside.

There are two bolts that hold the EGR valve to the intake. Plus, there is a big nut that connects the EGR tube (tube that runs from your right-side exhuast manifold to the bottom of the EGR valve) to the EGR valve.

Of course you have to disconnect the vacuum line from the EGR valve, and the electrical connector from the EVP sensor to remove it from the engine.

You can also disassemble the EVP sensor from the EGR valve and replace it independently if you just need that part replaced,without removing the EGR valve from the intake.

first i would check and make sure all the ac lines are ok. My stang throws an egr code cause i have the vac lines rigged up cause they broke