BenzWorld Junior Member
Date registered: Apr 2005
Vehicle: 1994 C220 >>110000 miles
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i have a similar if not the same problem. very rough idle that usually leads to stalling (and while the computer is trying to adjust the idle i can hear a strange "clunking or clicking sound" from the back underside of the car). even with minimal throttle the engine runs smooth and will not stall. however, my problem appears to be connected with the engine compartment being hot or not. usually the engine does not stall when it is cold, please note the word "usually". anyhow, after stalling the engine starts without any hickup, but may shut of again after 5 seconds or sometimes much longer. this problem started happening long time ago (over a year) much more pronounced during the summer months. initially i have gotten the usual advice: MAF, sparks, fuel delivery system and most recently the wiring. upon my purchase of two different MAF the problem remained the same. a new fuel filter, oil changes, throttle body cleaning, fuel pump check, did not resolve the issue. initially i have opened the MAF insulation and i found deteriorated wires that must have been shorting out (i did get one CEL code for this). i properly spliced, replaced wires and repaired that issue (with my original MAF) and the engine semed to return to normal idle, with miniscule idle fluctuations which i didnt like but was happy that my problem was as it turns out temporarily gone. the winter was good for this problem it seems, because it returned with full force this spring. upon additional inspections, i found a disintegrated rubber vacuum hose connecting from the pasenger side EGR valve to the vacuum changeover valve mounted on the front of the engine, and replaced it. Prior to this replacement i had a CEL code about incorrect air flow (dont remember exact wording). the replaced vacuum tubing (=12 inch long) seemed to pacify the problem once again. during all this time i have had noticed deteriorated wiring throughout the engine compartment. however it returned to haunt me again but without any CEL codes anymore, yet the engine idles rough and stalls continuosly. i got angry and pulled out the wiring harness and repaired it myself. i used military spec wires for temeratures over 200 degrees celsius. i must note that i did NOT find any wires shorting out (insides of the throttle actuator included) eventhough they were cracked and darkened all the way to the ecu plug. after replacing the engine harness the problem remains the same. my most recent idea was to check the EGR valve, and i did. the one on the passenger side works properly, yet the one one the driver side directly by the firewall seems to allow some exhause gas leaking into the intake manifold even when the valve should be closed. i am told that this can cause the problems i am experiencing. currently the valve is removed and its being cleaned and soaked in gasoline. tomorrow i will see if it leaks and mount it back to the engine.
after me writing all this does anyone alse have anything to add?? comment? i trully hope my experience helps other people and maybe someone can give me additional pointers regarding this rough idle / stalling problem. if the EGR does not resolve the issue i really dont know where else to look. :/
1994 C220, 108k miles