Here are a couple of suggestions. Search on throttle body cleaning. It has been suggested that cleaning that will solve low and erratic idle on 119 motors. (It helped mine). Also, the engine wiring harness is known to fail on these cars. Mercedes will replace it under good will if under 100,000 or 120,000 miles. I can't remember which.

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Bob Johnston
03 E55
Comand/Nav/Bluetooth/Ipod added
Black/black
(Oh man, this car is sooooo fast.)