GM Service Manual Online
For 1990-2009 cars only

This condition may be caused by one or more of the following problems:

    â€¢ Broken balancer or pulley hub. (Replace all parts.)
    â€¢ Loose torque converter bolts. (Retighten to specifications.)
    â€¢ Accessory belts too tight or nicked. (Replace and/or set tension to specifications as necessary.)
    â€¢ Exhaust system grounded. (Reposition as necessary.)
    â€¢ Flywheel cracked. (Replace flywheel.)
    â€¢ Excessive main bearing clearance. (Replace as necessary.)
    â€¢ Excessive rod bearing clearance. (Replace as necessary.)
    â€¢ Low quality fuel.