C36 problem - PeachParts Mercedes-Benz Forum

Fly Navy · #1 03-25-2006, 10:50 PM

Hi guys,
I have a '95 C36 AMG with a problem which I hope someone can help me with.
The car starts first time every time, and idles normally, however as soon as I put my foot gently on the gas pedal the revs drop and the engine will either die or it will catch just before stalling and suddenly speed up to where it should be. While the revs are above 1000 the car operates normally - no stalling or misfire, etc, but if I slow done to turn a corner, stop at traffic lights, etc and allow the revs to return to idle (about 500 to 700RPM), the problem manifests itself.
I had it diagnosed as a MAS problem and replaced it but there was no change. Even with the MAS disconnected the problem remains. The problem gets worse as the car warms up - first start of the morning it is almost gone. Please bear in mind that I'm in Australia where MB parts are very expensive, the dealers are bandits and the nearest one is almost 2 hours drive from my home. I've changed the spark plugs (unlikely I know) and looked for a vacuum leak. The wiring all looks good. I'm guessing it's the oxygen sensors or throttle body.
The car has only done 38,000 miles. I am the second owner. Any suggestions?

#2 03-26-2006, 12:46 AM

Check the engine harness connecton under the intake maniful .That may be water get in side. Un plug it & check for water. Hope this help.

Pete Geither · #3 03-26-2006, 06:28 AM

Sounds like it's a goner to me, but I'll be glad to take it off your hands.

Richard Wooldridge · #4 03-26-2006, 10:17 AM

Hi there,
It sounds like it's running way too lean, and the thing that comes to mind is a possible shorted temp sensor or wiring. The temp sensor should have a high resistance cold, going towards lower resistance hot. I'm not familiar with your engine, but this is the way most all systems work.

Fly Navy · #5 03-26-2006, 01:39 PM

Thanks for the replies. Richard, I'm interested in your theory but unfortunately I'm not too familiar with my engine either! Are you talking about the sensor which measures the coolant temperature? I have noticed that the gauge never reads above 80C lately but can't recall whether this is "normal". How can I test for this possible fault?

Richard Wooldridge · #6 03-26-2006, 06:45 PM

Hi again,
There are actually two temperature sensors - one is for the Temperature gauge, and the second tells the fuel injection computer how warm the engine is. On a cold engine the second sensor "tells" the engine to run richer, and as the engine warms up the resistance of the sensor decreases, telling the engine to run leaner. My thought is that if you have a wiring harness short that decreases the temperature sensor input to a very low resistance value the engine will run very lean. What we need is some more input from more knowledgeable members regarding your engine that can identify the location of the sensor in question. Of course, if it's a short in the engine harness it might be harder to find, or go away, or become intermittent.