Car vibrates when standing with A/C on

JOHNY84

MEMBER
2012 HYUNDAI I30
1.6L
AUTOMATIC

Dear all,

I have 2012 Hyundai with 1.6 petrol engine. To explain my problem:

When i'm driving with a/c on, every time I stop, the car starts vibrating (revs are normal). If I hit the gas, vibration stops. If put it in neutral, the vibration subsides. If I turn the a/c off, almost no vibration at all.

Anyone?

Thanks!

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

The AC puts an additional load on the engine. As a result, a sensor called the idle air control valve needs to increase the engine RPM's to compensate for the added load. If it doesn't function properly, it could allow the RPM's to slightly drop. Thus, you feel a vibration. You mentioned that the RPM's are okay. Are you sure they are not dropping with the AC on? Do a little test. Start the engine, let it idle with the AC off. While watching the tach, turn the AC on. Is there any change in RPM's? If there isn't, it could be a few other things such as a bad motor mount allowing vibration to be felt, a compressor that is going bad.