ok more than likely it is piston slap noise.very common for these 3.4J engines.the fix is to replace the 1 threw 4 pistons with a newer designed piston that has a coating on the piston to stop this noise.if you do NOT fix it there will be NO engine damage at all.just an annoying sound.some people can live with it and thats fine it will NOT harm anything.if it is driving you nuts and you want the noise gone you must replace pistons 1 threw 4.that WILL fix this noise.here is the bulletin for the noise.my X wife has a 2001 Malibu same engine making the same noise.she has well over 150k on it and no problems at all other than that noise
Cold Engine Tick Noise
(Replace Pistons) Models:
2000-01 Buick Century
2000-01 Chevrolet Lumina, Malibu
2000-01 Pontiac Grand Prix
with 3.1L Engine (VIN J - RPO LG8)
Some customers may comment on a ticking noise (similar, but not related to valve or lifter noise) that occurs 10-15 seconds after a cold engine start. The noise will last for 1 to 2 minutes, and will fade as the engine reaches operating temperature.
The noise may be caused by excessive piston to bore clearance during cold engine operation resulting from the specific piston design used in cylinders 1 through 4.
Service pistons for cylinders 1 through 4 will now be of the same design of those used for all production 2000 and 2001 for cylinders 5 and 6, and will have polymer coated piston skirts. Pistons in cylinders 5 and 6 are not exhibiting the described noise condition. Important
|^ ||Note that this is a customer annoyance issue, and does not affect the durability or life of the engine. |
|^ ||Removal of pistons from engine cylinders 5 and 6 is NOT necessary if equipped with polymer coated pistons. It is recommended to rotate the crankshaft until the piston skirt is exposed in the lower crankcase area for inspection. Replace pistons in engine cylinder positions 5 and 6 ONLY if there is evidence of damage to the polymer coating on the piston skirt, or scoring on the cylinder wall (heavy scratches) is evident. Detailed diagnosis of cylinder wall/piston skirt wear is discussed in step 4.|