I have an 03 grand prix with the 3.1. When the RPM’s get above 4000 the right side of the engine makes a rattling, like it’s dragging a chain. I know it’s not a spark nock and GM said “it’s suppose to do that”. I actually don’t think they even investigated this, probably because it was under warranty at the time. If anyone has any clue as to what this sound is please let me know, it just bugs the hell out of me.
Might be a stretched timing chain. How many miles on the engine?
Now it has 86 thousand, but it’s been doing this since 32 thousand.