I have thought the tach could be causing some of these problems but a local mechanic I use said no and something about the engine controls getting the RPM data from the distributor (don’t quote me on this one). I think I saw the CD manual showing the tach gets its data from the distributor. There is a plastic cap inside the distributor that is chipped around the edges. I wonder if something as simple as a piece of plastic (doubt it) or even a bad sending unit for the RPM’s could cause problems. I really don’t know how the tach or fuel pump relay gets that signal.

Steve
85 500SL Euro