Well, the mechanic said he hooked it up to the scanner, and found codes for the air mass sensor and the coolant temperature sensor.
He explained that these two sensors communicate with each other and the DME, and that one or both could be out.
He replaced the coolant temperature sensor for free, said the problem didn't reoccur, so I picked it up and drove it home, when the idle immediately started fluctuating again. It fluctuates so much at idle with the transmission in drive, that I have to put it in neutral to stop the car from jerking. It's so embarrassing.
Called Edmond (the Irish-looking Syrian) back and he declared that it must be the air mass sensor. A frequent replacement item for all Mercedes- new and used - he said, and had a stack of 4 or 5 on his bench that he's replaced within a week.
Dealer wanted $447, fastlane charged me $255 delivered next day air - early morning delivery. Phil even kicked in $10.00 for the early morning delivery.
I love this site and the Fastlane parts shopping experience. I tried crying to Phill about my problems, but he wouldn't hear any of it - he's got a used Cadillac he bought recently that needs a new engine! Yikes!
We'll see if this works.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".