MC7777

I'm working on a friend's 92 Cherokee and when it's at idle there's a knocking sound. I read several if not all discussions on the causes of this. I pulled the inspection plate off and all the flexplate bolts were loose. I tightened them with locktite fired it up and the sound is still there. So I pulled the tranny, put a used flexplate in and still have that knock. I then pulled the pan off and wiggled the rod bearings caps and several of them had play side to side. I noticed a lot of carbon built up on the caps and basically the whole inside. My question is if anyone really has followed through and repaired this problem cause it is all over the forums but no answer?

DJKnightmare

If they had play, then there's your problem. If you're that deep into it, then pulling the caps off, and at least checking the bearings for excessive wear would be my next step. I am right there with you. I get rod knock at higher rpms, but lower rpms, and my oil pressure drops to like 5 psi

ijeeep

My suggestions are if your in there already..study up on how to plastic gage bearing and consider throwing in a set of standard or .001 undersize.
Also don't overlook the possibility of timing chain slap making the sound.
Also piston slap / piston skirt slap can make sounds that mimic everything from collapsed lifter to knocking rod.

94zj318

With the 4.0's, "Piston Slap" is a common issue, especially when first cold-started. My '02 Grand Cherokee WJ has that issue, as ALL 4.0's will typically develop. Don't know if that's your friend's issue, but I wouldn't rule it out.

-Vince

avensis

Hi, did you manage to resolve your problem ?