Hi all I am new to the forum. Was wondering if anyone has experienced this problem with their c220. I have a 94 with no codes. The car idles in drive at about 500-600 rpm which seems low. When the car is cold the idle tends to be rough. No backfiring & when the engine warms the problem is still there, but less pronounced. My mechanic initially believed this was related to the transmission & replaced the kick down switch to no avail. Was thinking it might be the Mass air flow sensor. Any Thoughts?

 

This problem could be related to carbon build up on the valves, or another common one is tracking down the spark plugs ceramic insulator.

You may be able to change a coding plug if your car has one to compensate for carbon build up or engine wear. Also check it for a headgasket. This is another common item on a C220 of that vintage.

 

I had exactly the same problem but more pronounced. Mine was because I had a headgasket go and it was replaced badly. My mechanic changed the "knock sensor" which greatly improved the situation. I am currently adding Redex to petrol to remove the carbon build up. It is much better but still not correct. Let me know if you fixed yours, so I can try the same. Thanks

 

I have a 1994 C280 and recall this same symptom. I replaced the spark plug wires, and plugs. Also consider the Air Mass meter; I had to replace mine. Hope this helps.

 

i have the same problem, i had to mess around with the idling stick to make it rev higher so the car wont turn off. its weird though, when i press hard on the pipe that gets air to the part right above the idle stick, it goes back to reving normal and when i take the pressure off, it revs low.

 

have motor mounts looked at. common cause of rough idle at start wiothout check engine light, especially in colder weather.