OK, I got the car back and the rough idle is partially cured. What I mean by that is that the roughness is now a little less than half what it used to be. My mechanic looked it over and said he couldn't find anything really, so he took it out for a drive and said when he hit the gas all kind of black smoke came out the back and then it smoothed out pretty well. I've never gotten black smoke, so he really must have hit the gas hard.

I don't know if it could make a difference, but I notice he changed my oil cap. Maybe it was loose or worn and not giving proper vacuum. Either way the rough idle is reduce to the point where it is no longer shaking the car, but is noticeable if you are looking for it. Maybe I just need to drive it and clean out all the crud that had accumulated from the problem. I will keep everyone posted. So much for the dealer's idea of writing it off. My Mechanic only charged me $100 for his time.

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Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired