Chrysler Repair: low rpms, vacuum leaks, vacuum leak

Question
i just bought a 94 saturn sl dohc automatic trans and the car starts up fine every time but at soon as it turns on the rpms go up to about 2000 and it takes like 10 second for them to go down but then when i put the car in gear they go to low and the car shakes a lot and if i put the a/c on it gets worse and stalls but it stalls somtimes with the a/c off to but as soon as i give the car gas it drives perfectly this problem only happens when the cars idleing and i thought it was the ignition coils so i gave the car a tune up and changed all the fluids both ignition coils and plugs and wires but it made no diffrence any suggestions

Answer
If the idle goes up to 2,000 RPM then that sounds like a vacuum leak.  If it comes back down then either the idle control motor is compensating for the vacuum leak or the motor was the source of the vacuum leak itself and should be replaced.  

This idle speed control motor is responsible for allowing air to bypass the primary path air enters your engine.  It does this my opening and closing a passage to make airflow corrections to maintain a set idle speed (usually 800-900 RPM).  Turning on the A/C puts a heavy load on the engine and as such the idle motor is supposed to open the passage way up more to keep the car from stalling out while the clutch is engaged for the compressor.  Turning the steering wheel also puts a load on the engine and the idle is again corrected.  

Do you have a check engine light on?  Have you checked for vacuum leaks?  I would be suspicious of broken vacuum lines or even a bad idle speed control motor based on the description above.
Doug