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Old 04-07-2009, 04:38 PM
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Question please help... mystery problem

ailright,,, i have a 98 tj. with 110 thou. miles on it. but only 7,000 on newly rebuilt engine.

here is the problem(kinda hard to explain so ill do my best here and hopefully someone can help). for about a month now,, i can be travellin at bout 2-3000 rpms and if i go over a bump of any sort the jeep seems like it cuts out or something, some of the times when it does this the rpm gauge will jump up about 1,000 more rpm's. but not all the time.
all of this happens in about a milli second. then it just keeps driving.

now just yesterday it diid it in first gear when i wasnt quite up to 2,000 rpm's.

someone told me it might be a loose wire along firewall or at the coil or somewhere else. but if it was a loose wire would it make the rpm's jump like that. i would have figured that if it was a loose wire it would just be rpm's dropping.

whether the gauge is going up or not.. its hard to tell(because it happens so quick) whether or not when it happens if the jeep is pulling back or if it is jumping ahead...kinda seems like pulling back tho.

please help!! thank you.

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Old 04-07-2009, 04:43 PM   #2
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I'll take a shot at this...

You say it only happens after hitting a bump, most certainly wiring related.
Tach jumps, the tach in your wrangler is electronic...loose connection could make the tach erratic.

There’s not that much wiring to a wrangler so I’d definitely start with tracing your ignition wires and check your couplers under the hood.

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Old 04-07-2009, 04:48 PM
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ya the tach does jump.

but you can feel the jeep jump as well.
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Old 04-07-2009, 04:50 PM   #4
 
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i'd double check all the chassis grounds in the engine bay
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Old 04-07-2009, 04:56 PM
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Originally Posted by booger View Post
i'd double check all the chassis grounds in the engine bay
would a loose ground (or any wire) make rpm's jump up??
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Old 04-07-2009, 04:58 PM   #6
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Yup
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Old 04-07-2009, 05:54 PM   #7
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i had a similar problem. turned out it was the computer telling it to put out an over abundant amount on energy. it fried my whole electrical system. get it checked asap
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Old 04-07-2009, 07:35 PM
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you say similar problem...
what was your problem.

like i said earlier it only happens over bumps on the road.
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Old 04-08-2009, 03:10 AM   #9
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I'm probably oversimplifiying it but RPMs can only increase with more air so i would be looking at the throttle body and its linkage.

edit: just reread it... its just the gauge thats jumping and not the motor speed?
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Old 04-08-2009, 03:38 AM
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Originally Posted by ygohome View Post
I'm probably oversimplifiying it but RPMs can only increase with more air so i would be looking at the throttle body and its linkage.

edit: just reread it... its just the gauge thats jumping and not the motor speed?
it was the motor as well as the gauge.

i chased it down.. it turned out to be a loose connection on the coil.

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