At high RPMs (when I'm flooring it), I hear a knock or rattle noise in the engine as if I'm burning cheap gas or something. I always use 93 octane. I'm not sure if the acceleration hesitates when it happens because I always shift. I don't have an SES light. What do you guys think it is?

 

Ok...upon reading several posts...My guess is that I have the dreaded piston slap. Any opinions?

 

I doubt it's piston slap if it does it under hard acceleration. Piston slap is usually only when idling or under light acceleration when the engine is cold.

 

Oh snap...how would I ask the dealer about it? Like I said it's noticeable at high RPMs. They may think it's due to engine abuse or something.

 

just tell em when you go to pass on the highway it does it

 

Do a search for TSB's on NHTSA.com and you should find a service bulletin on detonation in LS1's. A buddy of mine had a similar problem on his 02 SS.