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1999 4.0l engine noise? Maybe you know?

Dalton99xj

NAXJA Forum User
Location
Texas
I have a 1999 XJ 4.0l AW4 4x4. 4Door. This jeep was sitting for 5 years. I put a battery, champion plugs, cleaned throttle body, TPS, IAC, MAP sensors. Also ran a little bit of seafoam through throttle body. Dumped rest in full tank of gas. Ran jeep for a few days. Then went on a 200 mile trip. About 100 miles in jeep went from 55 - 60 to a whopping 20mph. And very little power. I got to my destination the next morning went to start it up. There was a tapping noise. And if I brought the idle up above 2500 rpm it makes a rattling noise. I cannot figure out from where. I have a video of the start and sound.

https://youtu.be/_bVXex4YACM



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Is or was the Check Engine Light ON ?

What caused the loss of power, fuel issues, engine sensor issues, or mechanical issues ?

Approximately where is the noise coming from ? Is it a valve lifter, piston skirt, broken motor mount, basic engine misfire, or flex plate noise ?
 
AW-4 makes it a flexplate. Cracked flexplates and loose flexplate bolts are somewhat common.
 
Not sure on the power loss. Did find a line that was bad on the fuel line that connected to a box under the jeep in front of the fuel tank.

Ill have to look at the flexplate maybe it broke and only catching some of the time....

Sound seems to be coming from lower engine area but could be flexplate area.

Yes i need new motor mounts. Seen that today.
Transmission mount in good shape.


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I believe that box is a charcoal canister, how is your line bad?

An engine stethoscope at Harbor Freight may be helpful to you, it's like four bucks. it works pretty good.

Not sure what you think could be happening on the flexplate, all it engages is the starter. It's bolted to the torque converter/ crank shaft. If it's not catching there you wouldn't have a running vehicle likely.



The sound is frequent and without seeing metal on metal mount contact I'm leaning elsewhere.

Can you get a clip underneath?
 
A clogged catalytic converter will slow a vehicle down like yours did.
They also get very hot, sometimes red hot, and can also develop a
rattle after they cool off...

An engine that's run low on oil can seize.
it's possible the oil screen pick-up was clogged and starved the engine
of oil on the trip...especially since it sat for so long. (5 years?)
 
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