96 E300D surging/missing after filter replacment - Page 2 - PeachParts Mercedes-Benz Forum

Jeremy5848 · #16 04-11-2014, 12:58 AM

FYI, my post #13 is in error: removing the throttle flap in front of the EGR valve does set a code in the '96-'97 E300D. This version (OM606.912) has a pressure sensor attached to the intake manifold. The sensor detects the pressure change when the flap closes down; this is done when the EGR valve closes, so that more dirty exhaust gets sucked into the manifold. If the sensor does not register a pressure change, it rats to the computer and the code is set. I ended up putting the flap back. (The '95 E300 does not have this problem so the flap can be removed.)

Note to newbies: the flaps in the crossover and in the intake manifold need to be there. They "tune" the intake pipes for more efficient operation as engine RPMs change. The result is improved torque. Do not remove these two flaps and make sure they work. EGR crud will gum them up and they'll stop working.

Jeremy

VW1300 · #17 04-11-2014, 08:48 AM

Thanks Jeremy for clarifying, I was still under the impression the '96 model wasn't as smart at the '97.

I neglected to mention in my previous post that I took the car in to my indy to see if he could find the root cause of the issue - EGR? ECU? He's a pretty thorough guy and confirmed the ECU was operating correctly (which isn't to say there was something going on internally with it, it just opened and closed correctly), all of the flaps and vacuum were OK, and finally ordered in a remanufactured ECU. That did not solve the problem either, (was able to send reman ECU back so I didn't have to buy it), which also leads me to believe the issue resides within the EGR itself. He also told me apparently there are two versions of the ECU for my car, an "early" and "updated" version, he said I have the early version.

I feel like modding the ECU with the little air filter is a Band-Aid, but without further information on what the root cause may be, it will stay there.

I can also confirm that the flaps need to be there. I drove for a while with a faulty vacuum system and when it was finally repaired, the car really did seem more lively - the non-turbo cars need every single horsepower they can get.

DieselJim · #18 04-11-2014, 10:13 AM

Before my coolant leak I was having a problem with my newly acquired 96 missing before it warmed up consistent with this thread. I noticed it after I changed my dirty air filter and oil. Figure the air filter change probably increased the air flow. Maybe its just a coincidence. Would like to see what everyone finds.

The wires have been cut to the EGR but not capped.

VW1300 · #19 04-11-2014, 11:22 PM

Re: Cut EGR wires - Is your check engine light on? Also - rough running when the engine is cold is a classic symptom of the glow plugs or glow plug relay not doing their job - I believe the relay on this engine is designed to stay on for a few minutes after the car is running to help smooth out cold start ups.

The missing/hesitation I was experiencing was at highway speed, around 60-70 mph, the engine would hesitate and stutter. Startups and around town driving were unaffected, though milage suffered.

DieselJim · #20 04-14-2014, 09:23 AM

Quote:

Originally Posted by VW1300

Re: Cut EGR wires - Is your check engine light on? Also - rough running when the engine is cold is a classic symptom of the glow plugs or glow plug relay not doing their job - I believe the relay on this engine is designed to stay on for a few minutes after the car is running to help smooth out cold start ups.

The missing/hesitation I was experiencing was at highway speed, around 60-70 mph, the engine would hesitate and stutter. Startups and around town driving were unaffected, though milage suffered.

The check engine light comes on for the glow plugs but thats it. I have never had one miss because of glow plugs once started and running smoothly. I'm thinking its because the EGR is not being controlled. Ok, I guess I need to complete the EGR mods documented to properly resolve this issue

DieselJim · #21 04-15-2014, 09:46 AM

Quote:

Originally Posted by Jeremy5848

The '96 E300D (W210, OM606NA) is not "smart" enough to know that EGR has been blocked for testing purposes only. It will (mine will) not set a code unless the electrical connection at the top of the EGR valve (plug w/3 wires) is removed. Caveat: I have a very early '96 (s/n about 5000); it's possible that later in the 1996 production year Mercedes added more electronics. YMMV.

I blocked both the intake and the outlet of the EGR valve and left everything else alone. It looks perfectly stock but does nothing so the air intake pipes now stay clean.

BTW, with EGR temporarily blocked for testing purposes only, the "throttle" flap just in front of the EGR valve can also be removed. Its purpose is only to help suck more dirty exhaust through the EGR valve into the engine. Remove two screws and the flap can be pulled out.

Jeremy

So I'm trying to make it as simple as possible for my weekend wrenching. If you put in a solid gasket and remove the throttle flap that should be adequate to eliminate the EGR for testing purposes.