I have a 99 Z28 M6 and I have just noticed a new sound coming from my engine. When under a load: ex. In 6th gear @ 60 mph going up a hill I can hear a knocking type sound but only in conditions like those. Any other time it runs and sounds great. Could this just be some bad gas or is this the notorious piston slap? What exactly is piston slap anyway.
Thanks Brent

 

sounds like spark knock. When is 6th gear lugging up a hill the car is under serious load.

 

What do u mean by spark knock and is there any solution to the some what annoying sound

 

use 5th when going up hills

 

Use premium gas. If you are, then run some top-engine cleaner through your engine to remove carbon deposits.