hawkpfc2 - Thanks - I fitted six new seals (the black things that go around the injectors) but I couldn't get the plastic injector seats with rubber o-ring. Checked all and looked ok.

Peter - Thanks for your suggestions - I will check for leaks but I think I need to get a vacuum pump. The Haynes manual is absolutely hopeless at mentioning anything to do with the vacuum system. I just don't know what to look for.

The fuel mixture is something else that puzzles me. I tried adjusting what I think is the mixture control (allen key screw in fuel distributor) but when I turned the screw anti-clockwise while the engine was running, fuel started to leak out and I had to tighten it fully clockwise to stop that.

I am going to replace the spark plugs tonight (even though every mechanic says they are ok) and the coil tomorrow night to see if either of these make a difference.

Thanks for the suggestions - I will update progress.

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John

1983 Mercedes-Benz 280E 115k miles
1986 BMW R1100 GS 40k miles