1995 E320 Wagon - CEL Issue
 

Hello Everyone:

The Check Engine light came on due to a broken vacuum hose between the EGR valve and the small pipe that fed to the Switchover Valve. Replaced hose and then these codes came back on. The following codes were pulled from the car:

DM:
5: Exhaust gas recirculation faulty

Pin8:
39: Exhaust gas recirculation switchover valve - open/short to ground or B+

I already did the following procedures:

(1) Pulled Vacuum on the EGR side and caused the car to stall.
(2) The EGR pipe was cleaned 8 months ago.
(3) Wireharness replaced 18 months ago.
(4) Replaced Switchover Valve last year since I had the same codes as before.

I could not believe that the switchover valve broke after a year and I did hear the switchover valve click once I placed voltage on it. Just in case, I went ahead and ordered a new one and replaced it. Cleared the codes and the car seem to respond well (it's probably my imagination) and then, the CE light came back on with the same codes. Arrrggggh!

Is it possible that I may have a defective part? Anything else? Any assistance is greatly appreciated.

Cheers,
Clive

Clive, how was the EGR pipe cleaned 8 months ago? A MB tech advised me that he removes the intake manifold in order to access/remove the EGR pipe, then uses Berkebile 2+2 Gum Cutter to unplug the pipe. Inserting a flex cable from the EGR valve towards the intake manifold will not clean the EGR pipe adequately. Obviously it's a more difficult DIY job to do it the right way, and more costly to pay someone else to do it the right way.

I'm not the smartest guy, so you may not want to listen to this but... When I first bought my 1995 wagon it had 87,000 miles on it. The guy I bought it from said the check engine light would come on within a few weeks because of a faulty exhaust sensor (I think that is what he said). Sure enough, it did. So I brought it back and had him disconnect the check engine light somehow. I have 197,000 miles on the car now and never once had an issue related to that sensor. I listen to my car and pay attention to how it drives. I watch the oil pressure gauge etc... Never had a problem. When it runs rough I check the engine.

My 2 cents

I don't have any info in front of me, but does this model use the oxygen sensor to monitor EGR function? I would try to find what the computer uses to measure EGR function. Not really sure that it isn't a manifold pressure sensor that it uses.

Remember to keep an eye on the upper and lower engine wiring harnesses as 93-95 benzes are a ongoing issue due to biodegradable insulation that auto manufacturers were forced to use at that time.

Also the EGR needs alot of cleaning to get it clear for proper operation. Low mileage and low speed/idle operation only makes the problem worse. You have more buildup at low rpm(idle) then at highway speed. The low milage car you bought probably got great care but not everythng that is normal maintenance is on the tune up list ie EGR tube cleaning.

After a long time, I am now having the same CEL issues. I have rechecked the EGR and switchover valve and they are working.

Now, when shifting on reverse or drive, I can see the idle go up and down slightly and the car is "chugging".

Today, I felt hesitation while accelerating and it feels the car does not have much power. Spark plugs changed about 8K miles ago.

Any ideas what to further check? Your assistance is greatly appreciated.

Cheers

If it were mine under the shade tree, I'd swap in a known good OVP relay and drive it. Clean the intake manifold, drive it. If neither solution proved results, I'd start searching through postings with the keyword "Electronic throttle actuator" and the like. It is possible that problems on the intake side are manifesting as exhaust symptoms.

(This is of course after reading that the harness and egr and associated vacuum connections were all replaced and are currently not leaking.)