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Old 05-13-2011, 12:33 AM   #1
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TJ 2.5L Motor Knocking

I've had this jeep for a little over a year now.
2000 Wrangler TJ 2.5L Teraflex Lift, Auto Trans. running 33's.

When I first bought it, it was fine, no ticking or knocking or anything, ran fine.
Until I changed the oil.
At first it was not much of a knock, more like a ticking. I was told that a lot of
Jeeps get it, but over the next few weeks it got a lot louder. I took it to a few shops in which I've been told its everything from a sticky lifter to an exhaust leak.
It's a knock now.
The knock only comes around when it is cold or when accelerating, and you could barely hear it at all once everything has been warmed up and on the move. I've had the lifters changed out, new rod bearings, new distributor cap, new wires, plugs and used injector cleaners. flushed out the thing a few times with sea foam. I'm running a little thicker oil in it and some lucas oil so the noise isn't as noticeable. I think using the thicker oil has caused a little bit of a leak in the rear seal? Noise seems to be getting a little louder. Power has always been an issue (even for a 4banger) a few of my friends have had them too and all of them has more power than mine.
Just wondering if anybody has any ideas on what to do next?

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Old 05-13-2011, 07:55 AM   #2
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Check the flex plate (flywheel) for cracks or loose torque convertor bolts.

Either will give a ticking knocking noise, more so on accel and when cold.
Cracked flex plate after it heats up, metal expands, will quiet down slightly.

Easy check. In neutral, brake on, rev engine slightly and note noise.
Now in gear, brake on, rev engine. If it get's louder you may have one of those.
Pull the inspection plate off the bottom of the bell housing to check.

Take a flash light and look close where the flex plate bolts to the crank, and at the spots where the t/conv bolts to the flex plate. If you see lines radiating out or rust lines most likely you have a cracked flex plate. If not check the T/conv bolts make em TIGHT!



Also a cat converter going bad can cause a ticking/knocking, ditto a broken baffle in the muffler. Again more so cold and on accel. Goes away warm.

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Old 05-13-2011, 08:22 AM   #3
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Piston slap is normal for the 4.0 not sure bout the 2.5 if that's what you here.
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Old 05-13-2011, 10:06 PM   #4
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mileage odometer reading
how many miles on the motor ?
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Old 05-13-2011, 11:37 PM   #5
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i actually think i have this same problem. i am interested to know also. a buddy of mine said possibly a valve flap bouncing and the thicker oil(once heated) quiets it.
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Old 05-15-2011, 12:15 AM   #6
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Motor only has 90,000 miles on it. .. .
I think I'm going to check out the catalytic converter... I did some research and from what I've found it sounds like that might be whats causing it. When I first took the jeep to the shop I had a check engine light on.. they hooked the computer up and said I had something wrong with the 02 sensor... They reset the system and the check engine light went off, hasn't come on since. ... . hmmmm.... I heard that if you can cover your exhaust with your hand and hold it there, you have bad pressure, which can mean a bad catalytic converter, I'll try that and a hammer tomorrow. see what happens. The converter is there just for emissions right? If i cut it out will effect my engine? .. If this don't work I'm just gonna blast my radio so I dont' have to hear that knock, til i can afford an engine swapout. ... Thanks everybody!

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