1995 Ford Explorer EGR problems

I have a 1995 Ford Explorer - engine light comes on after a few minutes at higher speeds - code tells me 335 and 332. I have replaced the DPFE unit and the engine light went off for a month or 2 and now is back on. I have checked the EGR valve and it appears to be fine. Can anyone help me with this one? Thanks

Welcome to the forum!

How is it running? Smooth, normal idle, or rough high idle?

thanks for the response- I would say it is the idle is smooth and normal - in general, the vehicle seems to run well.

Well that may rule out the manifold gasket then, and then again it may not.

This may be your O2 sensors are bad. They are only good for 80-100 k.

Listen for a hiss/air leak sound around the manifold. Search for checking resistance on your O2 sensors.

I did not knowthe O2 sensors would affect the EGR valve - are there several of them? are they hard to repalce? where are they located if more than one? Thanks

Search button is your friend

Seriously, search for O2 sensor. Your question will be answered.

PFE or DPFE?

western5 said:

I have a 1995 Ford Explorer - engine light comes on after a few minutes at higher speeds - code tells me 335 and 332. I have replaced the DPFE unit and the engine light went off for a month or 2 and now is back on. I have checked the EGR valve and it appears to be fine. Can anyone help me with this one? Thanks

Click to expand...

Do you have a V6 or V8? I thought that all 1995 models were equipped with PFE instead of DPFE. See http://www.explorerforum.com/forums/showthread.php?t=256185 for a thread on PFE.

2000StreetRod said:

Do you have a V6 or V8? I thought that all 1995 models were equipped with PFE instead of DPFE. See http://www.explorerforum.com/forums/showthread.php?t=256185 for a thread on PFE.

Click to expand...

I had my PFE replaced with the new style DPFE under the recall at my local dealership.

Obd-i

I don't have the OBD-I System Operation Summary but it's probably similar to OBD-II.

code 335 is EGR sensor voltage out of range and code 332 is EGR valve opening not detected.

How did you check the EGR valve? Did you detect movement of the diaphragm as controlled by the EGR vacuum regulator?

If so, then I would check the DPFE output to the PCM even though you replaced it only a few months ago. With ignition ON but engine OFF check VREF. It should be between 4.0 and 6.0 volts. Then with engine cold (no EGR) probe between SIG and GND and start the engine. The SIG to the PCM should be 0.75 to 1.25 volts for the black plastic DFPE and 0.35 to 0.8 volts for the aluminum DFPE. These tests should pass since you're not getting code 334, EGR valve position sensor voltage above closed limit. As the engine (running faster than idle) warms up -Is your engine coolant thermostat functional? - the EGR valve should open and the DFPE voltage should increase to between 4.0 and 6.0 volts. This test will probably fail and is what the PCM is using to set code 332. If it does fail, then either the DFPE is bad or the vacuum source to the DFPE is incorrect.

Do you have a vacuum gauge?

EGR problems - 1995 explorer

thanks for the information - we used a vacuum testor while it was running and it interupted the engine (slowed it down) - when i had it apart i put a screwdriver in it also and it appeared to move properly inside - i will follow up on your suggestions - someone else suggested the o2 sensor which is not the first time i have heard that - i will look for the location and try to replce it too

sensors for EGR test

western5 said:

. . . someone else suggested the o2 sensor which is not the first time i have heard that - i will look for the location and try to replce it too

Click to expand...

For OBD-II, the required functional sensors for the EGR test are CKP, ECT, IAT, MAF and TP. I don't see how a defective O2 sensor could result in codes 335 or 332. When the EGR test fails for IAT greater than 32 degrees, a flag is set and the system and test are disabled for that driving cycle. If the failure is detected on the next driving cycle, the DTC is stored and the CEL is illuminated.

Your PCM thinks the EGR valve is not opening properly. Either it's not being commanded to open by the EVR, it's not opening, or the DFPE is not detecting that it opened.

thanks again = i will try to test the DFPE. When you mention the EVR valve where and what is that?

Evr

western5 said:

thanks again = i will try to test the DFPE. When you mention the EVR valve where and what is that?

Click to expand...

EVR stands for EGR Vacuum Regulator. It controls the opening and closing of the EGR valve via vacuum. The EVR contains a solenoid that is electrically controlled by the PCM.

I don't know what it looks like on your engine since I have a SOHC. But it's probably a black plastic looking module mounted on the intake manifold with one electrical connector on one side midway between top and bottom and two vacuum lines on the same side near the bottom.

Dpfe

just a little side line here....I was getting high Nox for a California smog test. Read many posts here...and finally replaced the DPFE sensor...didn't work...replaced egr valve and egr selenoid. Still had high Nox. So I went and returned the DPFE (it's the aluminum one), still had high Nox. So I read another post here that the aluminum dpfe sensor are junk. Well, they are, I replaced it with the plastic dpfe. Passed emissions this am with flying colors. Do spend the little extra money and buy the plastic DPFE. Will save tons of aggravation and actually money in the long run!

Thanks for all the help here!!

Scott