Could you tell us what year and model? Makes a difference -- the 617 engine, especially later turbos, has an idle shake problem that can easily be resolved. The 602 doesn't have either the problem or the easy fix!

On any engine with considerable milage, the engine shocks are probably bad, or engine mounts, or both -- this allows engine vibration to reach the chassis instead of being absorbed by the mounts and shocks as it should be.

You can check by watching the engine, hood up, when it shakes. If it wobbles at lot, suspect bad engine mounts, it shouldn't move all that much even if idling rough.

Check the location of the fan in the fan shroud -- if it is near or on the bottom, the mounts have collapsed -- they will look flat, and some of them are fluid filled, when they go bad they leak oil.

Engine shocks can only be tested off the car, but if the mounts are bad, the shocks usually have been beaten to death by the engine sitting too low.

The mounts on my "new" '72 280 SE had dropped at least an inch and a half -- one shock was bent (!) and the other had no oil in it. New mounts and shocks and I cannot feel and idle vibration at all, although I can see some in the engine (bad fuel and sticky injectors).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!