Babymog, thanks for the detailed technique. i will look into this ....

Mbzman, car has 180,000 miles. i replaced head gasket last month, and the head was serviced. car idles perfeclty and no vibration in the cabin. this only happens when the car is in gear at a traffic light. if i put it in neutral it smooths out.....wiring harness is good, plugs are new, the only thing i have not done is find someone to pull codes for me (i don't have a check engine light in my car)...............

t walgamuth, can you describe what the harmonic balancer does? the rumble is very subtle, i am the only one notices it. only at idle while in gear....

THANKS

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1993 300E, 2.8 M104 .....