NormanB, I notice a few months ago that the spark plugs were indicating a rich fuel mixture and at that time I felt then the loss of power. So I decided to have the dealer shop to check out the fuel system, and the O2 sensor was not functioning correctly, so they changed it out. But I still felt there was a loss of power, so I decided to check the compression.
After your first reply, I went out and check the spark plugs I just pulled (about 1000 usage) and again they indicate a rich fuel mixture. I have little knowledge of fuel system (HFM-SFI), and I have no idea why the plugs are carbon fouling? A friend named Ludwig from Germany told me to try the Bosch F9dc0 plug; I’m using Bosch F8dc4 that the owner manual indicates to use, but it also calls for F9dc0. Ludwig said MB went to the F8dc4 to improve the idle, however it’s a colder plug and may indicate a rich fuel system and the f9dc0 will burn the fuel better. I do remember my original plugs were f9dco’s. However the f9dc0 plugs are not available in the US, so Ludwig got the f9dc0 from Germany. I installed the f9dc0 today, and maybe it will correct both problems ??
I changed the fuel filter at 81,000m, I have 96,000m, but as you suggested start with the obvious things, so I’ll try the filter change after I driven with these new plugs for a 1000m.
Thanks, enjoy your drive, timreid

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timreid
1992 400E
euro lights
500E sway bars
210 16in wheels