Intermittent Idle Problem, A/c Related Options

[Poonicus]

Alright so since about 3-6 months ago I've had a rough idle problem whenever the a/c is on, but whenever the a/c is off the car is perfect and this is Texas I kind of need my a/c on. Whenever the car is at running temp and even cold it idles fine at 800rpm but whenever you turn the a/c on it will go up to 1100 or so and then it will shoot down to 100-200rpm and the whole car shakes. I was wondering if this was because of incorrect belt tension, a vacuum leak, bad iac, or because that's what the celica's do when the a/c is running. Any help would be appreciated.

[Poonicus]

I don't think that it would be the idle control valve but anything could be possible in my opinion with the car it vary well be that is has a vacuum leak. I think I might just redoing all the vacuum lines first because I've been wanting to that anyway to clean up the engine bay anyway. And thanks for all the help guys, sorry it took me so long to reply been busy with work...