I have an 01 Cherokee Sport with just over 100,000 miles on it and I'm hearing a moderately loud knocking whenever I'm idling. At around 1500 RPM I can't hear the knock but whenever I'm in park or sitting at a red light it is really noticeable. I just recently changed the oil thinking it might stop it, but it still does it. I don't really know where in the engine it is occurring because I can only hear it when I'm sitting in the car with the air and radio off.

If anyone has some tips that won't cost me much money that would be great!

Thanks,
Sgt.Arafak

PS: I heard somewhere that putting a little bit of ATF in the oil will help with this but I haven't tried it yet and I don't know if it is bad for the engine or anything.

 

First try to isolate the general area that the noise is coming from so we can help you with a better diagnosis. Top of the engine, bottom, toward the front, toward the back. My first thought would be to check the torque convertor bolts. They do have a reputation for backing out and making contact with the bell housing of the transmission. There is an inspection cover on the bottom of the bell housing that is easily removed to check. The first sign will be marks on the inspection cover itself where the bolt heads have rubbed on it. If they have backed out, remove them one at a time and reinstall them with with some Lock Tite to prevent it from happening again. Retorque each one to specs and reinstall the cover.

 

Mine 97 was dong the same thing, bearings were toast, I had to install a new engine.
Hoever if you have a sticky Lifter, the Trans oil may help.
I have used it a few times in the past on old Mopars and it works great.
Use about a half of a quart, pour it in with the engine running.