engine quits on low idle

[ambush276]

When i have the idle knob turned all the way up the car is really shaky until the oil temp gets about 60c, at which point it smooths out and is fine.

I did notice though if i start to move the idle knob down, the car shakes violently even at a warm engine. I can turn it down a little bit with no problems, once the engine is warm, but if i turn it all the way down it starts to shake violently and sometimes will even quit (even at a warm engine).

Is this normal?

If not, is this usually a sign of bad compression or something as simple as motor mounts or a valve adjustment (typical cases).

I know this question has been asked before, but not really in this specific light (at least from what i could search).

Thanks!