98 LS. Idle fluctuates from 1200-500 and sometimes lower

My 98 LS 3 door will idle anywhere between 1200 and 500 rpm, and im not sure what the reasoning behind it is. Also, occasionally the idle will drop to the last line before 0 and bounce off it like a reverse RPM limiter. when it does that i hear the A/C compressor turn on and off.

What could cause the idle fluctuations and what causes the sudden drop of the RPM?

Dirty idle air control valve.


Also, idle for these cars should be set at like 700-800 if I remember right.