GM Service Manual Online
For 1990-2009 cars only
    • Improper oil viscosity. Install recommended oil viscosity for expected temperatures.
    • Excessive piston to bore clearance.
    • Excessive piston pin to piston clearance.
    • Excessive crankshaft end clearance.
    • Excessive crankshaft bearing clearance.

Some engine noise may be normal for 1-3 seconds at start-up. Be sure that any noise that is identified is really coming from the engine. (i.e. ABS initialization noise)