GM Service Manual Online
For 1990-2009 cars only
    â€¢ Engine flywheel contacting the splash shield. Reposition the splash shield.
    â€¢ Loose or broken crankshaft balancer or drive pulleys. Tighten or replace as necessary.
    â€¢ Excessive piston to bore clearance. Replace the piston.
    â€¢ Cold engine knock usually disappears when the specific cylinder secondary ignition circuit is grounded out. Cold engine piston knock which disappears in 1.5 minutes should be considered acceptable.
    â€¢ Bent connecting rod.