Diagnostic Aids
WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.
The accessory drive components can have an affect on engine vibration. Such as, but not limited to, the A/C system over charged or an extra load on the generator. To help identify an intermittent or an improper condition, vary the loads on the accessory drive components.