99 civic idle goes up and down

I have a 1999 Civic 1.6 SOHC.
After it warms up for a few minutes.
The engine idle goes up and down.
It won't hold a steady idle.

Any ideas what causes this?

IAC (Idle air control) Soleniod, Map Sensor, TPS (Throttle Position) Sensor, Air Charge Temp Sensor. Just need to figure out which one is causing problems, or if any of them are and move on from there.

Also look around for a vacume leak. My car was recently doing what your's is doing and it was a vacume leak. Also make sure your PCV valve is cleaned up.