Engine knock diagnosis?
Thread Starter
Seasoned Member
Joined: Dec 2011
Posts: 372
Likes: 1
From: Springfield, MA
Year: 1993
Model: Cherokee
Engine: 4.0
<iframe width="420" height="315" src="https://www.youtube.com/embed/phpft11NzRs" frameborder="0" allowfullscreen></iframe>
93 XJ 4.0 auto NP231
Not sure if the vid works but here goes. I've had this noise since my engine swap. I swapped it with a block from the same year model but with less miles. I kept the original head and had it planed. I think it might be the flywheel but i really have no idea. You can see in the video that it sounds like it coming from everywhere. Thanks for any input in advance.
93 XJ 4.0 auto NP231
Not sure if the vid works but here goes. I've had this noise since my engine swap. I swapped it with a block from the same year model but with less miles. I kept the original head and had it planed. I think it might be the flywheel but i really have no idea. You can see in the video that it sounds like it coming from everywhere. Thanks for any input in advance.
CF Veteran
Joined: Aug 2011
Posts: 1,031
Likes: 4
From: Blue Springs, MO
Year: 1993
Model: Grand Cherokee
Engine: 4.0L Laredo
It's really hard to 'see' a noise with a video.. I'd get a stethoscope or at least a length of hose and try to pinpoint the noise with that. Put something solid in the searching end of the hose for better sound transfer. (a bolt or long rod) Watch out for moving parts.
*Just from the video, it could be a stuck lifter, but I wouldn't rule out a rod or crank bearing either. Post what you find out
*Just from the video, it could be a stuck lifter, but I wouldn't rule out a rod or crank bearing either. Post what you find out
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
It's really hard to 'see' a noise with a video.. I'd get a stethoscope or at least a length of hose and try to pinpoint the noise with that. Put something solid in the searching end of the hose for better sound transfer. (a bolt or long rod) Watch out for moving parts.
*Just from the video, it could be a stuck lifter, but I wouldn't rule out a rod or crank bearing either. Post what you find out
*Just from the video, it could be a stuck lifter, but I wouldn't rule out a rod or crank bearing either. Post what you find out

Thread Starter
Seasoned Member
Joined: Dec 2011
Posts: 372
Likes: 1
From: Springfield, MA
Year: 1993
Model: Cherokee
Engine: 4.0
So i was planning on doing the rod bearings so i bought a new 20% higher flow oil pump and the rod bearings .001 over. When i pulled the old oil pump i spun the gears and it sounded like s**t so i thought i got lucky with the noise just being a bad oil pump. So i replaced it with the high flow one and the noise went away! Problem is, it came back. It was fine for a couple of days but now its back and it's worse. Before i drive this thing off a damn cliff, anybody got any advice? thanks
So i was planning on doing the rod bearings so i bought a new 20% higher flow oil pump and the rod bearings .001 over. When i pulled the old oil pump i spun the gears and it sounded like s**t so i thought i got lucky with the noise just being a bad oil pump. So i replaced it with the high flow one and the noise went away! Problem is, it came back. It was fine for a couple of days but now its back and it's worse. Before i drive this thing off a damn cliff, anybody got any advice? thanks
Did you replace the bearings????
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Thread Starter
Seasoned Member
Joined: Dec 2011
Posts: 372
Likes: 1
From: Springfield, MA
Year: 1993
Model: Cherokee
Engine: 4.0
no i didnt. i pulled the pan and oil pump before i bought the bearings just to make sure i could check the size stamp if i did pull the bearings. When i heard how bad the oil pump sounded when i turned it by hand i thought i was set.
Thread Starter
Seasoned Member
Joined: Dec 2011
Posts: 372
Likes: 1
From: Springfield, MA
Year: 1993
Model: Cherokee
Engine: 4.0
Anybody? I have a new theory though. Could it be my distributor gears stripping out. Yesturday it was having trouble starting. Almost like it wasnt getting fuel but it could also be that it's not getting proper spark. It sounds like it fires on a few cylinders then no cylinders then starts all within 3 seconds when i start it. This morning it started like it came out of the showroom, before i could finish turning the key. It used to start like that all the time after i did the injector upgrade.
Thread Starter
Seasoned Member
Joined: Dec 2011
Posts: 372
Likes: 1
From: Springfield, MA
Year: 1993
Model: Cherokee
Engine: 4.0
Just put a long screwdriver up to the engine block just below the distributor and i can definitly hear something noisey. I'm not sure if thats how it is suppose to sound or not but i ordered a new distributor from auto zone. It was only $60 after the core. It will be here this afternoon along with my new track bar bushings. hopefully have them both replaced tonight.
Thread Starter
Seasoned Member
Joined: Dec 2011
Posts: 372
Likes: 1
From: Springfield, MA
Year: 1993
Model: Cherokee
Engine: 4.0
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