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..

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Current cars:
2001 MB E55 AMG
2003 Honda S2000
2000 Honda CRV

Gone but not forgotten:
2004 BMW 325i 5sp sport
1999 BMW 540i sport
1997 MB E420
1995 BMW M3 coupe

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.

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Fred Hoelzle