You are ignoring the obvious.

If the idle is fluctuating up and down, it means the mass air meter is struggling to find the proper mixture of air to fuel. It obviously can't.

This means that you either have a vacum leak somewhere in the system, introducing "false air" into the sytem, and preventing the mass air meter from working.

It also might mean that the mass air meter itself has gone bad.

Likewise, a faulty throttle actuator causes the same symptoms.

A problem like yours is very characteristic on this engine. It is always one of the three above issues.

Search the archives. There is tons and tons of info on your issue.

Last, take your car to a Mercedes specialist. The average run-of-the-mill shop will not have the expertise to properly diagnose your car.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".