Vibration Only In Reverse While Idling at Operating Temperatures - keywords 2.2 AC buzz engine gear hot idle L61 moan mount shake shim

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

On rare occasions, a vibration may be experienced while idling in reverse at operating temperature. It may also be noted that the vibration is worse with the air conditioning on. This vibration may be a result of mis-aligned powertrain mounts.

If the SI diagnostics do not isolate a cause for this concern, temporarily remove the center cushion bolt from the front engine mount and evaluate the concern. If the concern is eliminated, the front mount is most likely in a bind, limiting the rotation of the powertrain assembly when the transmission is placed in reverse.

Inspect the front cross-car beam of the engine crossmember for obvious, severe damage and repair as necessary. If the front cross-car beam is not obviously bent or damaged, shim the engine mount that is near the serpentine belt upward up to 3/8" where it attaches to the frame. If the concern is still present after shimming the engine mount, modify the front mount lower bracket that attaches to the engine crossmember by lowering the existing slots for the center mount bolt an additional 1/4". Once the slots are lowered, resettle the powertrain assembly by loosening all of the powertrain mounts, shifting the transmission from drive to reverse multiple times while idling, and retorquing all of the powertrain mounts with the transmission in neutral.

If the concern is still present, the engine crossmember may require replacement since it may be bent without any obvious damage.

Important: The front end alignment should be inspected and reset to specification after performing the above repair.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.