1991 Jeep Cherokee, 4x4,b inline 6 engine, Laredo edition
 

Just bought my Cherokee. Has a nocking sound coming from the engine area. Don't know exactly what is wrong with it. A friend said it was a piston but want to know if someone has a different opinion before we start pulling engine apart. Any ideas are helpful.

Welcome to CF Libromason !

Really hard to tell you what a knock is without hearing it. There are several things it could be. one yes is piston slap does it change when warm? is only at idle? only when hot/warm? :confused1:

Nocking sound
 

It sounds like a rock hitting inside the engine area. It's starts when the Jeep is warmed up and that's in idle. Also at low speeds. But if I hit the gas or drive at a higher speed roughly 30 mph it goes away. I've googled it and I found out it could be one of three things, flexplate bolts are loose? The converter is bad? Or a bad piston or valve stem?

My uncle who works on cars said its a piston or the flexplate. My friend thinks it's the valve stem.

First thing I'd do is tighten the flexplate bolts.

https://www.cherokeeforum.com/f51/ho...ocking-125547/