Engine trouble
 

I recently bought and 85 300zx non turbo and the car runs great most of the time. Every now and again though the idle will drop from 1000 RPM to 600-700 and the whole car shakes, but once I move and stop again it idles normal. I checked the spark plugs and wires and the idle control and they all are in good shape and seem to be working properly. Does anyone have any ideas what could be causing this problem?

Welcome to ZDriver!

It's supposed to idle at 750rpm for manual and 700rpm in drive for an auto I believe. First, get it to idle at the correct rpm (it's on a sticker on the inside of your hood). Possibly your throttle cable is sticking, or the butterfly needs the screw adjusted lower. Run some injector cleaner through the gas tank and do a tune up. Plugs, wires, cap, rotor, fuel filter, oil change, the usual. Any of these could cause a rough idle. If that doesn't work, you may need a engine mount. The first thing you do when you get a new (older) car is do a tune up.

I may be missing something, it's too early in the morning for me to be awake.

Thanks for the advice. I'll check all that stuff out and see if it helps.

also check your timing as it has alot of influence on idle as well.