well my g/f's car has a knock and i am wondering what does piston slap sound like and what would a rod knock sound like. Her car knocks at all rpms but if i remember right a rod knock will make the motor cut off hers never does. it has had such a knock for so long, over 2 years she says, i'm just wondering if its piston slap. tia

 

what year is the car? if its a 01+ the Exhaust lifters are Rhodes type and make that sound normally. Mine has done it from day one.

 

What kind of car does she have? LS1s are notorious for getting a carbon build up on gf's cars. They baby them too much. The same thing happened to my gf's C5 and it was carbon build up. A decarb took care of the problem.