I drive a c280 w/ approximately 123k on it. Recently, whenever I take the car out and then either put it in neutral or into the park gear, the rpm's will by themselves move from about 5-600 to about 1500 rpms.

Moreso, I noticed that if I turn the car on and keep it in park, this problem will not a occur.

On a side note, I just recently checked up on my spark plugs (which is probably one of the most time consuming things I've done). Could the aforementioned problem be a result of a loose insertion of a spark plug? I do not hear any misfiring though.

Any input is highly appreciated,

Conrad Kania
August 28, 2006