knocking 4.0

hi i was just wondering if anybody knows why these 4.0 motors
sound like there knocking while at an idle. I know several people
who own xj's and yj's and they all make the same noise idling
thanks in advance 1993 xj 120.000miles

my xj has239k miles.......best friend has one with 285k i believe and ours both do it.......always have. I think its just the way the inline six motor runs to be honest with you.

I bought my XJ 4.0L with 123K on it and it had the same knock you speak of. A mechanic told me it sounds like a wrist pin slapping, nothing to worry about. It now has 238K on it and the knock is still there, but still runs great.

He must have been right...

I just make sure the oil gets changed regularly, and of course, keep it tuned.

My 88 Cherokee Laredo does the same thing on a new Re-manufactured engine. Sounds like it is coming from the front of the engine. Have replaced the water pump, fan clutch noise is still there.

Jeep dealer mechanic suggested replacing the harmonic balancer.

Haven't tried it yet.

i have a 90 cherokee 4.0 and mine knocks all of the time, my cousin has a 97 cherokee 4.0HO and it has a small knock, and my other cousin has a 95 wrangler 4.0 and all of ours have knocks. and about the harmonic balancer, i had to replace mine, and it takes forever, but mine knocked before and it knocks today. you may try to replace but it didnt change mine

the 4.0 engine is notorious for this knock. there was some minor defect that i read about and cannot remember. they tried year after year to correct it which is why the later models do it less and less than the earlier models. I wish I could find where I read about it...maybe another post on this same forum.