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Engine Knock at Idle

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Old 03-06-2014, 07:52 PM
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Default Engine Knock at Idle

I have a 98 jeep xj with an AW4. I believe it has made this noise since I've owned it from 150k, has 169k or so now. I changed out the cracked exhaust manifold. That made the engine a little more quiet. I also tightened up the flex plate to torque converter bolts about as tight as I could possibly get them yet the noise is still there. Seems to be there hot or cold. It seems to go away under load and return at idle. I made a video because I know how vague it can sound when describing engine noises.

http://www.youtube.com/watch?v=Q7jLT...ature=youtu.be
Old 03-06-2014, 09:47 PM
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46 views and no one has a guess?
Old 03-06-2014, 10:07 PM
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Well, our 4.0's are noisy engines. Both of the XJ's that I have had made noise. How does it run? Any problems? If it runs good, just ignore it unless it gets worse. Lifter tick is very common. I have heard about piston slap or something like that but have never heard it.
Old 03-06-2014, 10:08 PM
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All I heard was a little lifter noise and louder exhaust manifold noise.
Old 03-06-2014, 10:14 PM
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if you hold the brake and put it in gear.. does the sound stop?
Old 03-06-2014, 11:08 PM
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Originally Posted by scottmphoto
Well, our 4.0's are noisy engines. Both of the XJ's that I have had made noise. How does it run? Any problems? If it runs good, just ignore it unless it gets worse. Lifter tick is very common. I have heard about piston slap or something like that but have never heard it.
Runs great just like it always has. So each 4.0 to their own pretty much? some are noisier than others and such?
Old 03-06-2014, 11:08 PM
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Originally Posted by bigbadon
All I heard was a little lifter noise and louder exhaust manifold noise.
So nothing really to be concerned about?
Old 03-06-2014, 11:09 PM
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Originally Posted by JackJare9455
if you hold the brake and put it in gear.. does the sound stop?
No I don't think so.. does it anytime it idles.
Old 03-06-2014, 11:18 PM
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Here is a news flash: engines make noise when they're running. Some make more noise than others, but a 4.0 will make noise for 500k miles when others won't.
Old 03-06-2014, 11:19 PM
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What kind of oil and filter are you running?
Old 03-07-2014, 12:10 AM
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Mine makes the same noise. That slight knock.... You have to hear past all that ticking and valve noise to hear it.... It's been doing it ever since I've owned it, i haven't had any problems and don't think I will. They are loud engines.
Old 03-07-2014, 12:34 AM
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Runs like a champ. Don't even stress it. If it gets louder change your exhaust manifold and or collector gasket. Also check for cracks in header and what not.
Old 03-07-2014, 12:36 AM
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This is mine.
Old 03-07-2014, 12:36 AM
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I put "Cherokee knock" into U-Tube search and found ME, (11 down)>>

Not identical, but similar to yours. It's been doing that for well over 10 years. It's part of the reason the previous owner sold it to me in 02. Please use a Wix filter. or napa Gold, (same thing). Not Fram, the "Orange Can Of Death"
Old 03-07-2014, 12:41 AM
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Where you been Flintstone? Miss your input.


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