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Unread 02-16-2003, 02:39 AM   #1
andymigs
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4.0 L rattle during idle

Hello,
I have a 94 Cherokee 4.0 4x4 with 155,000 mi. For the past year or so I've been experiencing an occasional rattling noise during idle. The noise is significanlty worse when the compressor is on (I'm guessing it is the additional load). Also, there is often an associated shudder/CLANK when starting or shutting off.

This noise is best described as "sounding like there is a bolt (or marbles) sloshing around in the crankcase". It is a low pitched chunk/clank, shuddering, metal-on-metal sound which appears to be coming from the very rear of the engine or torque converter.

My Torque converter suspicions were strengthened when I removed the flywheel covers and realized that the 6 bolts on the flywheel were scraping a nice circle on the backside of the covers. The holes in the flywheel thru which these bolts mounted were "stretched" i.e. not round, but eliptical in the direction of rotation. This observation explained a different, pinging noise that recently prompted me to get under the hood. Obviously, i'm getting a new flywheel, but I think the idle problem may be something else.

Has anyone experienced this before? A mechanic said he was certain that it was coming from bad pushrods, so I'm guessing it is probably in the converter or transmission. I pulled the rods, they looked fine.

I'm pretty comfortable under the hood, as are most of my friends, who are all a bit stumped. Thanks in advance for any help.

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Unread 02-16-2003, 11:17 PM   #2
Jerry Bransford
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When catalytic converters break up inside, as they do, they have a mean rattle that is often especially bad when the engine is at idle.
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Unread 02-18-2003, 09:04 PM   #3
wildvan
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If the rattle kind of reminds you of a diesel engine at idle, then it is semi-normal for the 4.0 during the 92-94 year range, mine rattles at idle, but runs great, if you bump up the octane, it helps, but with the gas prices, put up with the rattle. If the noise sounds like marbles, then good luck and keep hunting..
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Unread 02-19-2003, 03:34 AM   #4
andymigs
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Marbles, that's it

Thanks Wildvan,
I think we have the same problem. I've been ignoring it for a long time, and it has become intolerable. Hopefully yours won't get to this stage anytime soon. There is a fine line between the "diesel option" (as we call it) and something which draws strange glances from other motorists and "what is wrong with your engine" comments. Mine has crossed that line.
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Unread 02-19-2003, 07:26 AM   #5
wildvan
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If it has gotten that bad, then here is something you will not like, I talked to the jeep dealers and also called Chrysler, they all said it was normal. and the only way to get rid of that problem was to replace the head. They quoted as saying it was due to the valve train. If they are correct in what they are saying, then you may need to A) try overhauling the head you have or B) Buy a new head. Before this, try to increase your octane and see what happens..
Hope it works out, remember, there are some nice big valve heads out there
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