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Old 12-18-2012, 10:11 PM   #1
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Help! Engine ping/knock

Howdy,
So I've got a 1999 TJ with the 4.0. It's got about 153,000 miles on it and has had an oil change every 3000 miles and every other preventive maintenance issue that I can think off. In about the past 10000 it started making this noise on occaision. It'll only do it if its been starting cold and it always stops after the engine warms up. The wierd thing is that it is not consistent. I may go a month with not a peep. Then the next month it happens 2 or 3 times. I haven't really been able to pin down any rhyme or reason.

Ever since i noticed it I've been putting in midgrade fuel and ran a few cans of seafoam through the gas tank(not in one sitting, over a few tanks of course).

I also went ahead and replaced the spark plugs, wires, distributor cap and rotor.

Still hearing the noise. Any thoughts on the cause and solution? Anyone else had something similar on their 4.0?

See video for the sound, make sure its turned up, the sound is the important part, nothing visually important in the video.

https://docs.google.com/open?id=0B6I...ndXMkZVdjdZWUU

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Old 12-19-2012, 12:58 AM   #2
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Quote:
Originally Posted by thebaconator View Post
Howdy,
So I've got a 1999 TJ with the 4.0. It's got about 153,000 miles on it and has had an oil change every 3000 miles and every other preventive maintenance issue that I can think off. In about the past 10000 it started making this noise on occaision. It'll only do it if its been starting cold and it always stops after the engine warms up. The wierd thing is that it is not consistent. I may go a month with not a peep. Then the next month it happens 2 or 3 times. I haven't really been able to pin down any rhyme or reason.

Ever since i noticed it I've been putting in midgrade fuel and ran a few cans of seafoam through the gas tank(not in one sitting, over a few tanks of course).

I also went ahead and replaced the spark plugs, wires, distributor cap and rotor.

Still hearing the noise. Any thoughts on the cause and solution? Anyone else had something similar on their 4.0?

See video for the sound, make sure its turned up, the sound is the important part, nothing visually important in the video.

https://docs.google.com/open?id=0B6I...ndXMkZVdjdZWUU
thebaconator,

First off love the display name lol BACON!

On your engine have you taken note if it's burning oil? Have you had to add any oil in between oil changes? Seen any blue smoke rolling from the exhaust? Let me know and hopefully we can get a better ideas of whats going on there.

Phil

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Old 12-19-2012, 10:01 AM   #3
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I haven't noticed any signs of burning oil. No smoke from the exhaust pipe and i've not had to add any oil either. I can check later today if there are any other signs to look for, but right off hand I don't think that's happening.
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Old 01-13-2013, 09:33 PM   #4
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I have the same thing with my 03 jeep can't really figure out what it is. Was thinking either the water pump or the belt tentioner but just like you it's hit or miss when it happens but goes away quick sounds like something in the fan let me know if you figure it out
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Old 01-14-2013, 03:18 PM   #5
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I have an '02 doing same thing....almost sounds like a lifter.
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Old 02-13-2013, 11:14 PM   #6
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Fixed it!

I started reviewing all my regular scheduled maintenance and realized I was due for a new serpentine belt. I googled serpentine belt noise and found a handful of youtube videos that sound just like this. Long story short I replaced my serpentine belt and its been quiet ever since. For those of you in a similar boat give that a shot if you haven't already. I also found a few folks suggesting idler pulleys make a similar noise although mine turned out to be fine.
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Old 02-13-2013, 11:19 PM   #7
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Yep, always check the idler and tensioner pulleys. I pulled my belt today, and found that the bearings in the idler and tensioner were both junk, and neither was audible with the engine running. It literally takes 5 minutes to R&R the belt, so those of you that haven't checked your pulley bearings, do it now so you don't have a failure at the worst possible time. Or, the best possible time. It's just another one of the things that should be checked. The ol' "if it ain't broke, don't fix it" saying doesn't hold true if you simply didn't know it was broke.
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Old 02-19-2013, 08:15 AM   #8
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Will give it shot.....thanks for your input.
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Old 04-29-2013, 11:46 PM   #9
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Originally Posted by Patrick H View Post
Yep, always check the idler and tensioner pulleys. I pulled my belt today, and found that the bearings in the idler and tensioner were both junk, and neither was audible with the engine running. It literally takes 5 minutes to R&R the belt, so those of you that haven't checked your pulley bearings, do it now so you don't have a failure at the worst possible time. Or, the best possible time. It's just another one of the things that should be checked. The ol' "if it ain't broke, don't fix it" saying doesn't hold true if you simply didn't know it was broke.
Dumb question but how can u tell the pulleys are bad? Too much play maybe
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Old 04-29-2013, 11:54 PM   #10
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Dumb question but how can u tell the pulleys are bad? Too much play maybe
Pull them off and spin them by hand. You can hear and feel if the bearings are bad. They should be smooth and quiet.

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