I not sure, but my pops car had a similar problem a while back. It would seem that the engine was missing, and was not idling smoothly. You could notice it more in drive than in park. No lights came on, but found out later that the egr valve was bad. Since the mixture was out of wack, the engine was not idling properly.

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2002 G500 74K
1998 E300 200K and rising
1995 S600 73k


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