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Old March 19th, 2007, 10:14
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engine bucking under acceleration!

91, 4x4, auto,179k,4.0,stock everything.
A few months ago I went through a mud hole and it got pretty deep. The engine died but started right back up again. I cleaned water out of air box, replaced filter,dist. cap and rotor,spark plugs, and fuel filter. The problem I have is that whenever kicked down or under heavy accleration Xj cuts out and bucks. I let off the gass and it's back to normal. Everyday driving is fine, but whenever I go to pass someone or take off fast it does it. It seems like it only does it about 2 outta 3 times. I have never had a check engine light come on, I check codes anyway and they were clear. Is there some sensor that normally get damged when going through mud or water?
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Old March 19th, 2007, 10:23
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Re: engine bucking under acceleration!

Sounds like ignition. Most of the sensors won't leave you hanging. For instance, on the Renix, even if you lose the engine speed sensor in operation, it'll approximate position from the dist sensor.

Hard accel makes demands of of spark, and a weak spark shows up like you describe. I would check wires first. If older, you may have separated it internally in taking them off and/or bending them around to clean. A common place is at the spark plug boot. I've seen this on lots of other cars as well.

-Skip
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Old March 19th, 2007, 10:39
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Re: engine bucking under acceleration!

You mention speed sensor? I replaced mine and it went out in 3 mos. I just said screw it, when I get a ticket I guess I'll fix it. I guess I'll do wires this weekend and see if it helps. Also my neutral safetey switch has been out since I bought the Jeep. Sometimes it wont turn over so I bump the shifter and it starts right up. Could this have anything to do with it?
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Old March 19th, 2007, 19:37
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Re: engine bucking under acceleration!

The speed sensor is on the bell housing and it won't start without one...

The only ticket you could get without one is illegal parking...
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Old March 20th, 2007, 04:11
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Re: engine bucking under acceleration!

I have replaced speed sensor once and it went back out. What's up with that? The speed sensor is on the outside of the transfer case. What kinds of problems could a bad sensor cause? I have been driving it for a long while with no speedo. Are you talking about neutral safety switch?
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Old March 26th, 2007, 10:40
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Talking Re: engine bucking under acceleration!

I figured it out! My muffler was wasted and leaking, I put on a new muffler and the Jeep never ran better.
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Old March 26th, 2007, 11:32
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Re: engine bucking under acceleration!

I can't see how that would help, unless the problem isn't as described... A 'leaky' muffler will just keep you from passing a emissions inspection. However, if old and the baffles have somehow sandwiched together, it would choke on higher rpms, but that would include highway cruising.

In rereading your posts, it sounds exactly like a clogged fuel filter - especially the sock in the tank. Did you happen to move anything there? Of course, if it's a filter, it will show up, then go away, then show up, etc until it gets really bad. And most likely on a trip...

Let your tank get really empty, then fill up (doesn't actually have to be a full tank fill) with the pump handle at full flow. This will stir up any crud in the bottom and if driven right away, will continue to fill the filter screen. If it happens again, then you know it's the sock in the tank. Replacing is easy, and all the crud comes out with the sock...
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