Originally posted by John_Schwarz
My guess is either fuel delivery or vacuum.
I agree. It has to be a fuel supply / pressure problem or a very slight vacuum leak that is hard to find.
Remember, my terrible oscillating idle problem turned out to be a vacuum leak at the intake manifold seal, but it only occurred after the car had reached operating temperature.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".