4.0 engine noise

[Morks]

Interested in seeing what you find.

Have you checked the oil pressure with a test gauge?

Yeah, I mentioned it before its low. Had a mechanical gauge on there, and from the first start until operating temperature its normal psi. The first time I drop it in neutral or really bring it below 1500 rpm the oil pressure drops and stays low like 5psi at idle and only gets to like 15 at most when running. Or if I run down the highway I get like 20-25 min of great oil pressure then it starts fluctuating.

 

[JKP]

Definitely low. The PCM turns the check gauges light on and chimes when below 6 PSI on my 06

 

[Morks]

Definitely low. The PCM turns the check gauges light on and chimes when below 6 PSI on my 06

Mines on quite a bit

 

[Morks]

Well popped the oil pan just now and a couple of small shavings in the oil pan, going to start popping (rod or main?) bearing caps off, and hopefully find the culprit(s)... Rods are straight as can be from the plain eye and spinning the engine I can't see any piston slap...

 

[oconnef]

Well popped the oil pan just now and a couple of small shavings in the oil pan, going to start popping (rod or main?) bearing caps off, and hopefully find the culprit(s)... Rods are straight as can be from the plain eye and spinning the engine I can't see any piston slap...

Curious to see what the result was?
I have an 06 TJ with 275k miles and the sound is most like yours. I've been chasing a misfire in cylinder 1 (only) and the plug looks fouled by carbon but no wet oil or anything. (Dry) compression showed 120psi on all others - but cylinder 1 at 65psi. Gonna do wet compression next - I got stopped by the rain too. And leak down if that doesn't tell me anything. I'm hoping it's not the piston, but I don't want to do a lifter, rocker arm, pushrod job unless it fixes the issue. Hoping the leak down will reveal the culprit or I'll be pulling the oil pan next as well - though I'm admittedly not a pro at this level of mechanical work.

 

[Morks]

Curious to see what the result was?
I have an 06 TJ with 275k miles and the sound is most like yours. I've been chasing a misfire in cylinder 1 (only) and the plug looks fouled by carbon but no wet oil or anything. (Dry) compression showed 120psi on all others - but cylinder 1 at 65psi. Gonna do wet compression next - I got stopped by the rain too. And leak down if that doesn't tell me anything. I'm hoping it's not the piston, but I don't want to do a lifter, rocker arm, pushrod job unless it fixes the issue. Hoping the leak down will reveal the culprit or I'll be pulling the oil pan next as well - though I'm admittedly not a pro at this level of mechanical work.

Hey, mine was a rod bearing! Ended up putting a rod through my block. The motor was trashed at my own fault. Lost out on a super clean 03 Inca gold rubicon as the motor blew on my way to go grab it

 

[oconnef]

Hey, mine was a rod bearing! Ended up putting a rod through my block. The motor was trashed at my own fault. Lost out on a super clean 03 Inca gold rubicon as the motor blew on my way to go grab it

Oof! Double whammy! I’m calling the shop tomorrow just to see, but I have still have a suspicion it’s the exhaust valve. I just don’t know the state of it…

Got all the tools for the service bulletin mentioning stuck valves in 4.0L model, pulled the rocker arms and pushrods. The only thing of note so far is the pushrods are not bent, but they are absolutely CAKED in crud.

 

[Morks]

Oof! Double whammy! I’m calling the shop tomorrow just to see, but I have still have a suspicion it’s the exhaust valve. I just don’t know the state of it…

Got all the tools for the service bulletin mentioning stuck valves in 4.0L model, pulled the rocker arms and pushrods. The only thing of note so far is the pushrods are not bent, but they are absolutely CAKED in crud.

I am no engine guy, just a kid working on a jeep. However, those are dirty lol. I ran mine for a year with basically no oil pressure and they were cleaner!