Hey guys, my 91 Cherokee Laredo (4.0 6 Cylinder) has a pretty distinct knock coming from the engine, previous owner had it like this throughout the whole time he owned it and never gave him any troubles, jeep still runs like a champ. was just wondering if anybody could possibly tell me what the knocking is from, maybe one day in the near future i'll look into it. The car has 226,500 miles on it by the way, and still runs better than my mothers Mercedes of my stepfathers F-150, who is on his 4th transmission right now, that's right, 4th transmission. Nice job Ford.

 

I'm not an engine expert by any means but I have an XJ with a knock as well. Not as pronounced as yours, but the "pattern" seems similar. Many people think mine has a sticky lifter. Does the problem come and go? Does it go away when the engine is warmed up? Check flex plate and torque converter bolts too, that's what others have suggested to me. I asked a couple mechs if it was piston slap and they all said no because the problem is irregular for me. But if it is consisten, then it may be piston slap, which I have heard isn't really gonna hur these XJ's? Someone else will come along and yell at me if I'm wrong, I'm sure Here's a vid of mine:


EDIT:

This is a second vid I made, it might be easier to identify. Like I said, ours seem to have a similar rhythm...

 

Nope, tick is there the whole time, warm or not. the only time you don't hear it tick is when its above 1000 rpm. if it is a piston slap then i wont even bother with it, that's just too much money to spend on an old jeep like this one.

 

Do this to eliminate it as a possibility.

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

 

X2

Also check it the flexplate for cracks. Good method found here:
https://www.cherokeeforum.com/f51/ch...xplate-172081/

This noise was caused by loose torque converter bolts for me.

 

I'll take sticky lifter for $1000. Goes away when the oil pressure rises enough to finally pump it up. Try running some MMO in there for a while to see if it cleans things up.
Piston slap goes away or at least lessens when the engine warms up and clearances are reduced unless you broke a skirt- but your recording does not sound like a broken skirt, nor would that go away at higher rpm. It sounds like a stuck lifter hammering.

 

Very well could be. OP should shine a light in the oil filler hole and check how much sludge is in there. MMO, a quart, with an oil change and good filter next. If it ticks on initial start, shut it off and restart in 20 seconds and see what happens.

 

mine sounds exactly the same as yours does Andrewenglish...i would like to get rid of mine as well. I take extra precaution and chance my oil like every 2k miles, with some Lucas additives...i have had people tell me its a rod, lifters, piston, bla bla...i hate it though

 

It it was a rod, it would have gone through the block by now. Have you checked your torque converter bolts? Lucas is exactly what NOT to use for suspected lifter issues. MMO, one quart and run the **** out of it a few times.

 

amen

 

Lucas will restrict oil flow,causing oil pressure to rise a little and making you feel better while killing the engine.

 

Grasshopper,

Piston slap is irregular. Your vids sound as though you have piston slap.

Piston slap can end up putting a connecting rod through the side of the crankcase.

And fix that vacuum leak I hear.

 

I knew someone was gonna yell at me!!

Piston slap is irregular? I meant irregular in the sense that, on a cold start on some days there is no noise, other days there is. It comes and goes as it pleases, no pattern. I didn't mean irregular as in the noise it makes. I thought piston slap would be more consistent then that, and then start to fade as the engine warms?

 

Would the noise coming from this problem increase with rpms?

 

Who knows? Just check them. It's a known issue and you can eliminate it. Takes half an hour. We can't hear your noises from where we're at. You need to eliminate some possibilities on your end and quit trying to get us to guess.