Rough At Idle
 

I recently purchased a 2002 Mercedes C240 Elegance from a small dealer with 80kms on it. I purchased it with one year warranty and have been having the same problem over and over again with the rough idle.

When I am at a light or just parked in idle it feels very rough. The computer does not pick it up and does not fire any codes out. I have had the spark plugs changed as well as the coils looked at. I also has the throttle body cleaned and the engine mounts checked out. I wonder if it may be the MAF sensor because I seem to be having poor gas mileage. I am lost and the dealership who I bought it from will not look into it unless it fires off a code. I have spent a lot of money at other benz repair shops and nothing.

Any suggestions?

They checked engine mounts and transmission mount? Trans mount can be over looked at times and cause vibration.

They told me the mounts were fine. Also do you not think it could be a sensor maybe MAF car seems like it will die sometimes?..

if you feel the vibration in your seat then its possible that the transmission mount could be bad. they sag over time and even if it doesnt fix your particular complaint your having, you might notice some differnce after you replace it. pretty cheap like under 100$ and easy to install probably an hour at the dealer. if the place you went to, to have it checked out looked at the actual values while idling he would be able to see that there is some slight missfire. if he says he not seeing a misfire then you might not have one. try using better gas maybe , put a tank of premium in and try it.

Yes the vibration is in the seat and the door and the peddle. It is in with Mercedes now but even they said because no lights are on, and none have come on it may be hard to pinpoint the problem. I would love it to be just the tranny mount but highly doubt full. For one the car is slow to take accelerate and seems like sometimes it will die as well as the poor gas mileage. I am thinking it could be a sensor but even that would come up. I am filling the tank generally with 91/94 octane nothing lower.. I am lost...

There are a lot of things that can be wrong with it. Take it to another dealer or make sure another tech at the same dealer looks at it. Just because there isnt a stored code doesnt mean there isnt a problem. MAF can be out of range, spark plug, plug wire, coil, fuel delivery can all be problems. Just an example, low fuel pressure wouldnt set a Check Engine light.

Rough At Idle
 

I had a similar problem with my C230 idling rough. It drove me crazy trying to find the problem, since the car did not display a check engine light or codes. I found the problem by accident (was not looking ). It turned out to be a small hose that became disconnected. Air was leaking from the vacuum hose. The hose is located near the oil filter cartridge. Your car my have this hose connected already, but the point here is that it could be a hose some where under the hood. So, I suggest you look over the entire motor and check all your hose connections to make sure they are not leaking or disconnected.

same
 

Wow same problem on a c 240, just replaced the tps and throtle 2 days ago and still have some prob, i replaced all the hoses that feed to the throtle and maff basicaly all the in da back area, i have an account at the dealer so only spent like 40 buks on them, im trying one more thing tommorow, let u know the results soon,

Hey,

I was just wondering if anyone knows if a throttle body from a w202 c200 would fit the newer model of the c200 w203 coupe?

Kregg

just bought my 2005 C230K and shortly after purchase I installed a K&N air filter...Awhile after it started vibrating when in gear at a light...I read where K&N filter oil can coat the MAF sensor and foul it...I went to Autozone and got a can of MAF sensor cleaner and cleaned the sensor..I got a lot of performance back but still vibrating...Thinking it was ignition issues I took it to the dealer for diag..They found the frt motor mounts collapsed but not broken...I had them replaced and the car is so smooth now that you cant even hear the motor running and it shifts very smooth now...If your car is close to 100k miles just do them regardless because they go out shortly after 100k anyways...Im happy with the car now and no other problems...