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Old 06-27-2003, 08:25 PM
suginami suginami is offline
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Join Date: Dec 2001
Location: Southern California, U.S.A.
Posts: 8,508
You may have read my post on the fluctuating idle. My fluctuating idle was exactly what you are describing.

My problem was a vacum leak - at the intake manifold - which is quite an unusual place for a vacum leak.

A vacum leak (anywhere in the system) is "false air", and prevents your mass air meter from figuring out the proper air / fuel mixture. The idle will hunt up and down, trying to find the right mixture, and can't because of the vacum leak, and keeps hunting.

If you don't have a vacum leak, then your mass air meter may simply be defective.

Additionaly, a defective throttle actuator will exhibit similar symptoms. The throttle actuators have pentiometers that go bad over time. They also have a wiring harness that goes bad - just like the engine wiring harnesses that fail in all M104 engines from 1993-1995.

At any rate, there are too many variables: take it to the dealer or an independent mechanic that specializes in Mercedes Benz vehicles.
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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".
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