I wanted to start a new thread because there were several I had been following that had so much contradictory advice I thought a clean start might be useful.
First, my symptoms:
Ran fine when cold. After it warmed up, it still ran fine if I was moving at all, but when I came to a stop it would give me a shake that would visibly move the car. My oil pressure would drop to about 2 also. If I stepped on the brake and just rev'd a tiny bit the pressure would pop up and the engine would smooth out. Sound familiar? If so, you will know that it isn't really a rough idle, more of a full on shake.
The Fix:
I replaced the rack damper pin (idler adjustment pin). It takes two wrenches, first you loosen the collar, then unscrew the old pin. Switch in the new pin and begin screwing it in. So far I only did a first pass on adjusting it. I expect I can probably get an even smoother idle if I keep playing with it (Hmm, wonder what I'll be doing this weekend), but just with a rough job the car is perfectly passable.
For the record, my other plan for the weekend is to do a valve adjustment as that was one of the other suggestions for smoothing things out, and I have no idea when it was last done as I haven't owned the car that long. After reading all the arguments back and forth about whether the rack damper would help or not, I almost didn't try it. I can't promise it will fix your problem, but just wanted to add my 2 cents. It fixed MY problem.
Thanks to all the good advice I read before trying this. I wish I had listened sooner.
A pox on all the rack damper nay sayers! Okay, not really. As a diesel newbie I appreciate any advice. I remain amazed there is such good advice with such poor descriptions of the problems.

-adam

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'84 300D Turbo Diesel
San Jose, CA