81 300SD Turbo Ive got an engine shake that happens only sometimes. I'll pull up to a light, and sometimes it idles just fine, others it shakes the whole car.

Im not talking about a vibration - but the engine just shaking on its mounts and rocking the whole car a bit.
Ive already changed all the fuel / air filters, and run some stanadyne injection cleaner directly into the pump, but it stll does it.

If i adjust the idle up to about 900 - 1000 rpm it goes away - but thats not really an idle
and when its shaking sometimes, i can put it in neutral and rev the engine lightly and it goes away, but not always.
it always idles just fine in the morning but after I take a few trips, or drive for 20 miles or so it will start to do it.

I looked around the forum a bit - but didnt come up with anything
What should I check? I'm at a loss for things to try here!

thanks!

-Dan

 

This question should be in the diesel forum. problem could be the rack dampner inside the injector pump.