Vibration on Idle on A/C is on

[hueyhy]

My car is 03 civic si with 119k miles.
When I turn on the Air conditioner, the car starts to vibrate (when idle)

Some told me it is because the IAC is not functioning properley to add more air to the engine to compensate for the extra load from A/C. Is that a possible reason? How can I check if it is the IAC or not?
Will it help if I clean the IAC? somebody said to use the carb cleaner, is it OK to use the throttle body cleaner to spray and clean the IAC? I suppose either would be good?

Thanks guys.

[talonXracer]

You will always get additional vibrations when you turn on the A/C, it is a compressor.

[hueyhy]

You will always get additional vibrations when you turn on the A/C, it is a compressor.
I know that. but the vibration is too fierce, it's like the whole car is shaking.
BTW I don't have mount inserts installed.

I know for some cars, when you turn on the AC, the idle speed goes up. but for my car, it stays still. is that normal?

[talonXracer]

The idle speed should stay constant or only bump up 50-100rpm's, when the A/C is turned on it causes additional load on the engine and the IAC increases the amount of air and ECU more fuel to MAINTAIN the idle rpm. And yes some engine systems do indeed bump up to a fast idle speed when the A/C is turned on. The compressor or it's pulley could be going bad.

[hueyhy]

A mechanic told me my alternator is going bad coz is making some noise, and I may need to get a new alternator (not the pulley). Is the bad alternator a possible reason for such vibration?
PS: i tested and found that if I turn on the headlight, there's also a little increase in vibration, suggesting that the "trigger" is a load increase for the alternator (may not be the compressor pulley).
I tried to wiggle the alternator's pulley when the belt is loosen, it is firm.

yes you also mentioned that when the AC is on, the IAC will let more air go into the engine to keep the rpm. does that mean if my RPM is stable, the IAC valve is functional, and the problem is somewhere else?(the compressor, alternator, or some pulleys?)

[T_Virus]

how's your motor mounts? stock, aftermarket?

[hueyhy]

how's your motor mounts? stock, aftermarket?

I recently changed the mounts, all are OE replacement mounts, "Anchor" if you know the brand.
But I guess the excessive vibration with AC is abnormal, because when AC is off, the vibration is moderate and acceptable.

[T_Virus]

I have the Avid motor mounts and when the AC is on with the Fan kicking in, it really vibrates but without the AC on or the Fan kicking in then there is a small acceptable vibration.