Low idling speed would cause the compressor to cut in and out. Jump starting or replacememnt of the battery could cause the PCM to reset and this can cause the idling speed to be affected. Recheck the idling speed and if it is too low, get the throttle body and IAC cleaned to stabilise the idling speed.
Unless the vibration is felt at all speed ranges and conditions, it is safe to drive the vehicle.
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Monday, September 21st, 2009 AT 2:09 AM