2006 making unusual vibrating noise

Whenever the AC is on and the car is idling, a vibrating sound is noticeable. The vibration becomes annoyingly loud when drive is engaged. The noise stops when we either turn off the AC or accelerate past 900 RPMs. The AC compressor was replaced, but problem remains unchanged. Any suggestions?

I think you may have a idler pulley or tensioner that the bearing is getting bad.

Whoever changed the AC compressor should have found this when they diagnosed the compressor was the problem.
But don’t be too hard on the mechanic…sometimes these are hard to pinpoint until it gets worse.



Tentioner, idler pulley and serpentine belt were all replaced with the last 12 months. We’ve kept it maintained by the dealership.

The problem might be with a dirty/defective Idle Air Control valve.


The IAC valve controls the engines idle speed depending on the load imposed on the engine while idling.

You can try cleaning the throttle body/IAC valve to see if it helps.

If not, the IAC valve probably needs replacement.


Thank you for your insight. We shall try that.

We have a 3.8L v6




It could be a loose exhaust shield resonating at certain engine RPMs.

Pop and hood and see if you can hear where it is coming from. Use a length of garden hose or vacuum hose as a stethoscope. Besides the ideas above, it might be associated with the radiator fan. It turns on when the AC is turned on.

Radiator was replaced about 18 months ago. Hose stethescoping sounds like a great idea.

Thanks y’all.