yesterday i aquired a 1992 cherokee-
owner said he had new engine put in, he
was told by mechanic he used different sized
pistons, sounds like a rebuild- at any rate
jeep does have some knocking- does it make
sense for larger pistons to create knocking
and if so is there a way to quiet/fix w/o new motor?

 

Can you post a video of the noise? The 4.0 isn't a quiet engine, they are rather loud and noisy normally.