my Benz is running great, but idle is unstable and car shakes??
 

my 97 E420 runs great, and I'm getting 24MPG on the highway @ 80MPH. However when the car is sitting at idle, the car is unstable, shakes around and the rpm would bounce around. any idea what might be wrong?? again the car is running great when moving.. :confused:

I suspect your fuel filter may need replacement.

ProV1, you also may need new engine mounts. With your foot on the brake put the transmission in "D" then press the gas pedal lightly while someone watches to see if the engine shifts position. Then do the same thing with the transmission in "R". If the engine changes position the mounts are shot and need to be replaced.