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Okay, this rattling noise in my engine is killing me. Not sure if it's spark knock, a bearing, or what.

'93 4.0, 145K miles.

Symptoms: Rattling noise at high (2500 +) rpm's in 3rd, 4th, and 5th gear. You can run it up to 3500 rpm's in 1st and 2nd gear with no noise. That would make me think that load has something to do with it. In the higher gears, maybe it's pulling a larger load, thus causing the problem.

It also get's more pronounced if you're pulling a trailer with some weight on it.

It kind of sounds like shaking a empty paint can with that ball in it, very fast... T-T-T-T-T-T-T-T....

I spoke with the jeep mechanic of our group, and he suggested I put some 20W50 oil in it to see if that helps with the problem. I'm going to do that tonight probably.

Does spark knock/pre-detonation happen at all rpm ranges? Does load have any effect on it?

Thanks!!

I actually tried to record the noise it's making, but it came out really bad. If you want to try and hear it, click on the link and turn your volume up a little. You have to listen real close and you'll hear it in the background.

Click on Engine Wav

[ 09-28-2001: Message edited by: DanH ]
 

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Since it does it only when loaded, it sounds like pre-ignition or detonation to me... run a tank of premium gas through it and see if that helps.

If the higher octane rated gas cures it, you might have carbon build- up in your combustion chambers or your timing might be off (advanced too far).

HTH,
Jake Harsha
 

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If the motor has a carbon buildup from age and mileage - I read a post from CJDave - I think - on the offroad board. Used a windshield washer to inject water into the running motor - says it is very effective on carbon removal. You might find him on the other"good Board" and E him. My .02 says try it and prem. gas.
Luck
Merlin <IMG SRC="smilies/smokin.gif" border="0">
 

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It does sound a lot like pre-detonation(engine knock), which is extremely bad for your engine. Back out of the throttle when you hear it happening. You need to drop down to slightly colder plugs, or at least close the gap by .005 - .010, and retard your timing in slight decrements untill the noise is no longer present under heavy load.
You will give up some HP, but will prolong your engine usable life substantialy. Better gas is also helpfull.
 

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By the way guys, I don't thing there is such a thing as "predetionation".
Gas is suppose to "burn" and not supposed to "detonate" (explode) which is the bad thing we are refering to ...
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Check your rocker arm straps..sometimes they break..just a thought <IMG SRC="smilies/usa.gif" border="0"> <IMG SRC="smilies/usa.gif" border="0"> <IMG SRC="smilies/usa.gif" border="0">
 
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