Hello Everyone,

I recently purchased a 2003 E500 with only 36K miles for my mom to drive and I am having some problems with the way it is running. Basically upon gentle acceleration between 35-40 MPH I feel a strange vibration like the engine is "shuttering" or running rough at that speed only. I do not notice it while decelerating or if I am accelerating quickly it is also not apparent. Also it only seems to happen after the car is fully warmed up. I can feel the vibration on my foot through the gas pedal and also any passengers can notice it as well.

Two weeks ago I took it to my trusted Mercedes independent mechanic and he said there were no codes showing. We decided to change the spark plugs and wires and that did help quite a bit but the rough running is still present. Also I have since had the tires rotated and balanced as well to rule that out.

Also when I feel the vibration I watch the RPM's and there is no fluttering etc. Someone mentioned maybe motor mounts but I can't imagine that would be it because the problem seems to happen only at the specific speed range.

One other issue I am having is during normal driving I will occasionally hear a "thump" sound coming from somewhere behind me. The trunk is empty and I made sure the spare tire and tool kit were completely secure. I cannot seem to figure out where that sound is coming from! It happens at the strangest times that are not necessarily associated with sudden braking or pot holes in the road etc.

Hopefully someone can chime in here who has lots of experience with this car

Thank you!!!
Jerome

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05 E55
03 E500