If the car had a misfire on one cylinder, did he try replacing the coil wire boot?

Did he try swapping coil wires?

This is a very basic and simple issue that usually has a pretty inexpensive solution.

You need to find a new mechanic and quick.

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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".