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92 Cherokee Problem - Flex Plate

9

92xjdean

NAXJA Forum User
Location
MO
Hi all,

I am completely brand new to this forum, so bare with me! I just purchased a 1992 Cherokee 4 dr. with the inline 4.0 engine, automatic, 4 whl drive. It has 168,000 miles on it. I don't know any history of the vehicle. The engine sounds good and it drove good when I bought it. I have put around 200 miles on it and now I have what sounds like a light rod kocking coming from down in the back part of the oil pan. Some interesting observations made so far are...when I take off from a dead stop there is a vibration that comes up through the floor and can be felt in the steering wheel and floorboard. It's also got a harsh noise accompanying the vibration. The best way I can describe the noise is that it sounds like a noise that if you tried whistling from your throat, deep and harsh but not quite a whistle. The noise and vibration are only present in the lower gears and it is sporadic, doesn't do it everytime. OK, now back to the "rod knocking" sound. Sitting idle, at around 800-900 rpms, it sounds just like a rod knocking! Now I have read where if you remove the spark plug wires on each cylinder while running, you can pinpoint the rod in question.....tried it, didn't work....but I got the shit shocked out of me! I have also read where flex plate bolts have been found to be loose and/or the flex plate/flywheel is cracked. I have also read where people have checked the motor mounts and/or transmission mounts etc. as a possible cause .....anyways, sorry for all of the details....I like to be as thorough as possible. Can anyone offer any suggestions? I plan on taking the bellhousing cover off today and checking the flywheel bolts......man I hope this is it!

Thanks Everyone for any replies!
 
is it leaking trans. fluid? becasue if it is that is a sign that the tc bolts are loose. i had the same thing happen to my 92
 
92xjdean said:
Hi all,

I am completely brand new to this forum, so bare with me! I just purchased a 1992 Cherokee 4 dr. with the inline 4.0 engine, automatic, 4 whl drive. It has 168,000 miles on it. I don't know any history of the vehicle. The engine sounds good and it drove good when I bought it. I have put around 200 miles on it and now I have what sounds like a light rod kocking coming from down in the back part of the oil pan. Some interesting observations made so far are...when I take off from a dead stop there is a vibration that comes up through the floor and can be felt in the steering wheel and floorboard. It's also got a harsh noise accompanying the vibration. The best way I can describe the noise is that it sounds like a noise that if you tried whistling from your throat, deep and harsh but not quite a whistle. The noise and vibration are only present in the lower gears and it is sporadic, doesn't do it everytime. OK, now back to the "rod knocking" sound. Sitting idle, at around 800-900 rpms, it sounds just like a rod knocking! Now I have read where if you remove the spark plug wires on each cylinder while running, you can pinpoint the rod in question.....tried it, didn't work....but I got the shit shocked out of me! I have also read where flex plate bolts have been found to be loose and/or the flex plate/flywheel is cracked. I have also read where people have checked the motor mounts and/or transmission mounts etc. as a possible cause .....anyways, sorry for all of the details....I like to be as thorough as possible. Can anyone offer any suggestions? I plan on taking the bellhousing cover off today and checking the flywheel bolts......man I hope this is it!

Thanks Everyone for any replies!
Click to expand...


You might have more than one problem.
THe knocking sound at the back of the oil pan might be the oil pump pickup tube. It is located in that position and is known to come loose occasionally.
hope this helps.

Jeff-97XJ
 
a timing chain knock is common on the 4.0 also.

My boss's 92 xj has been knocking at idle since he bought it 4 years ago... still sounds the same and it has 30k miles more on it.


the squeak and vibration sounds like a bad u-joint in the rear shaft. remove the shaft and rotate the joints by hand.
 
I just pulled the bell housing cover plate off. No loose bolts, damn it! I then took a long plastic tube and used it for my stethoscope, the noise is definitely coming from the engine area and not the tranny......question, can bad rod bearings cause a vibration????? Another question, can someone point me in the direction of what to do to install the rod bearings? I mean I know how to install them and what I am looking for are those little tips maybe unique to a jeep or any little helpful hints I may not know of.......thanks everyone, I'm bummin'!!!!!
 
I also just pulled the belt off, someone said it might be the water pump....no luck....but at least I'm narrowing things down!!!!!!! I'm convinced it's the rod bearings..........any other opinions????
 
Rod bearings usually go before mains, but if it's only one or two the spark plug trick should tell you which cylinder.

The flex plate could be cracked. Typically, that makes a rapping noise at idle in neutral. Put it in drive with the brake on, give it just a LITTLE bit of throttle to load the tranny against the brakes, and the noise should quiet down. If yours acts like this, suspect the flex plate.
 
I bought some "Restore" engine lubricant and put it in. Well, it's definitely in the engine, the noise that is. The Restore product did quiet it down quite a bit and also confirms to me that it is not the flex plate.....just wanted to share. It's a simple $8 check versus messing with the flex plate..........I guess new rod bearing are in my very new future.........
 
I still would check the flexplate for cracks, use a long pry bar or screwdriver and pry on the plate. The noise that a cracked flexplate makes can be very deceiving .
 
Hay dude with 167.000miles you should have a complete reman done or different motor put in. just changing rod bearings don"t get it .Your crank is out off round and new bearings will not stay I"ve had good luck with jasper reman motors and some good warranty like 70000 miles.
 
I've read plenty of messages in here where guys have put new rod bearings in and that was all that was needed............


dale rose said:
Hay dude with 167.000miles you should have a complete reman done or different motor put in. just changing rod bearings don"t get it .Your crank is out off round and new bearings will not stay I"ve had good luck with jasper reman motors and some good warranty like 70000 miles.
Click to expand...
 
If your engine runs good (other than the knock) and it has just started knocking, you should be able to get away with replacing the rod bearings. I doubt that your crank is "out of round" and replacing/rebuilding the engine seems a bit extreme unless it is absolutely necessary. I know that I personally cannot afford a new engine every time the old one has a problem.
 
92xjdean said:
I have what sounds like a light rod kocking coming from down in the back part of the oil pan.
Click to expand...

Well the light knocking is somewhat typical of the 4.0l engine, especially for that year. Seems Chrysler bored the cylinders a hair larger than spec and it causes a piston slap noise when the engine is cold. Jeep even had an official recall if the customer complained loud enough. Just about all of the 4.0 engines I've heard have a real light knock at idle. If it doesn't get worse, don't worry about it.

The vibration could be front drive shaft or axle ujoints, front wheel unit bearings, or a number of other things. Does it seem like it's related to wheel speed or engine speed?
 
What’s your oil pressure? If you pull your oil pan to replace rod bearings I would replace main bearings, oil pump and rear main seal also while in there.
 
I agree with this, I don't want to put a lot of money in this thing!


slowride63 said:
If your engine runs good (other than the knock) and it has just started knocking, you should be able to get away with replacing the rod bearings. I doubt that your crank is "out of round" and replacing/rebuilding the engine seems a bit extreme unless it is absolutely necessary. I know that I personally cannot afford a new engine every time the old one has a problem.
Click to expand...
 
The vibration is related to engine speed. In park you can rev it up and the vibration hits. Theres also a noise that comes from the bellhousing area. It's kinda like a whine.........does the piston slap go away after warmup? My light knock stays around after warmup....Thanks.

lawsoncl said:
Well the light knocking is somewhat typical of the 4.0l engine, especially for that year. Seems Chrysler bored the cylinders a hair larger than spec and it causes a piston slap noise when the engine is cold. Jeep even had an official recall if the customer complained loud enough. Just about all of the 4.0 engines I've heard have a real light knock at idle. If it doesn't get worse, don't worry about it.

The vibration could be front drive shaft or axle ujoints, front wheel unit bearings, or a number of other things. Does it seem like it's related to wheel speed or engine speed?
Click to expand...
 
I only have an oil light on my Jeep. What's the best way to read the oil pressure without the inside guage?

Cox89XJ said:
What’s your oil pressure? If you pull your oil pan to replace rod bearings I would replace main bearings, oil pump and rear main seal also while in there.
Click to expand...
 
Hey all,

I wanted to post a follow up to my 2 year old post. I'll tell you what, I drove the damn Jeep for over 15k miles with the noise I originally thought was a rod bearing. It did not effect the engine at all and I ended up taking the advice from someone, can't remember who, to just keep driving it, they all make the noise. I don't know if that was wise advice or not but in my case it was and the jeep was still driving great the day i sold it last month!
 
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