Same thing happened to me....
It has many things to do with that: Air Intake Hose could be bad(holes, not on tight enough, etc..), Air Filter could be not on all the way, the idle speed control motor or adjustoment is acting up(bad, sticking or needs to be adjusting according to your rpms, should idle about 1k-1300k rpm's) now if it's stick, screw off those the sensors, they should be black, theirs two of them, and spray, just ONE, only one small squirt of Carberautor Cleaner into each hole. Too much of it, will cause your ISC motor to go bad, so just one tiny squirt will fix that. It's a lot of things. If you have a Mass Air Flow sensor that could be a really, really big problem too, and that's an exspensive part, :(. Anyways, get back to me on this. pez