Matt:

That is exactly what I was thinking of.

However, you need to do the following first: Check engine mounts -- if vibration is significantly less in reverse than in drive, fix mounts, they are bad (the left one, I think, lasts longer because engine torque pounds the right one down more).

Verify that you have good injectors (minimal smoke, good starts, good milage, no serious knocks).

If every thing is fine, but you have excessive vibration at idle only -- goes away completely if you open the throttle even a little, the rack bolt needs to be adjusted. It isn't the bolt, really, it's the spring on the other end, but to fix that requires an IP rebuild ($1200 or so at least, and why rebuild the pump for just rough idle?).

Proper procedure is to make SURE the engine is at full operating temp, in drive with the brakes on hard, plus parking brake (you don't want it to run away from you driverless!), then unlock bolt and slowly screw in until idle smooths out JUST enough for you to tolerate it. You aren't going to get is totally smooth, most likely, and if you overdo it, you won't be able to start it cold.....! Lock screw down, then bump the throttle hard, then recheck idle smoothness. If still too rough, adjust in some more. It is very necessary to run the engine up against the brakes to check -- leaving it in neutral will result in under correction.

If you then have hard start problems, the spring is so bad you will have to live with the vibration until something goes bad enough in the pump to justify an overhaul, or replace the pump.

Remember, a bad engine shock will look just fine, but no dampen vibration -- they are much cheaper than pump repairs! So are engine mounts.....

JMH:

Occasional is how this starts out, usually it gets progressivily worse with time. Bad mounts will do the same thing, especially later gel filled types.

19022:

The 601 has gel type mounts, replace them and your problem will most likely go away. The mounts are ovalish when good, spherical to flattened when bad, so if the look droopy (or leak oily stuff), replace them. Do the engine shock, if you have one, at the same time.

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!