I recently aquired a 1992 300E with 50,000 original miles from a family friend. The car ran really well for a while and then I ran into this persistent problem.

The car will be running smooth and all of a sudden I will feel a flat spot, sometimes I can accelerate through it and sometimes it's like there is no power at all. This seems to happen most often while driving in town (stop and go traffic) although it has also happened on the highway. I have had to press the accelerator 3-4-5 times until I finally get a response, it will run smoothly for a while and then act up again.

I have replaced: fuel injectors, fuel pump, filter, spark plugs,wires, rotor, valve seals, head gasket, isolated and flushed the fuel system, even flushed the transmission. The car ran very well for a few thousand miles and now I'm having the same problems.