I recently bought this '03 C230K. When the car is not in gear the RPM's will drop, then it will rev itself up to around 2000 to 2500 rpm and repeat the process. It does not do this when I have it in a gear. I haven't taken it to the shop yet. It has 45K miles. Any thoughts?

A huting idle when out of gear sounds to me like an Electronic Throttle issue. Coming from Volvo in the past, I saw that OFTEN- more so then i should have... As well, it could POTENTIALLY be an Air Mass Meter (Or Mass Air Flow Meter as some people refer to it) or the Oxygen Sensors. How is your gas mileage? I would get it to the dealership for review. Is there a check engine or check engine electronics to coincide with the problem???

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There are no malfunctions listed. The gas mileage is getting 33 mpg HWY and 27 mpg City.

I really like the people at Import Specialists here in Springfield, MO. They have a mechanic named Dave Shipman that has been working on Mercedes for over 25 years.

He hooked the car up to an electronic tester computer (don't know the exact name) but his first incilination was that there was a vacuum leak somewhere.

The car had try to compensate for the problem by adjusting itself, so the adjustments had to be reset. He finally found it by spraying something around the vacuum lines while the engine was running. When spraying near the intake manifold he found the problem.

The gasket needs replaced on the intake manifold. The part is $7 and the labor is $450.

I haven't had him fix it yet. I hope this may help others.