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Discussion Starter · #1 ·
i have a 1999 tj with 4L. check engine light came on on the logging road. engine cuts out alot, more when hitting bumps. any ideas??. the code reader said cylinder 5 misfire. it gets alot worse when its cold and wet.
 

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check spark plugs, wires, and distributor cap.
you need a tune up if they are more than 30k miles old.
 

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Did the 99 model tj come with a distributor? Must be an Australian thing cause all of ours had coil packs.

Could be a loose connection. Or fuel related. Might need to run a spanner over all the earth leads. Or need a new coil pack.
 

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I have a 99 too and it has a distributor. Using the code...i would suspect a plug wire or the distributor cap, but like suggested, if it's been a while since a tune up I would replace the plugs, wires, rotor, and distributor. Take the distributor cap off and look at the rotor. If it's rough or carboned up change it all. In my experience with my own 99, that should fix it.
 

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Discussion Starter · #7 ·
well i check the plugs and the distributor cab and they all look good. cant seem to figure out whats going on. its almost like someone turns the key off for a split secound then on again???. very anoying when driving
 

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Discussion Starter · #9 ·
never realy when i have my foot into it. just when im crusing. even when im coasting down a hill it will cut out
 

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PAWheeler said:
i have a 1999 tj with 4L. check engine light came on on the logging road. engine cuts out alot, more when hitting bumps. any ideas??. the code reader said cylinder 5 misfire. it gets alot worse when its cold and wet.
I had a similar experience which I eventually worked out resulted from using E10 Fuel (10% Ethanol) Once I returned to using standard Unleaded Petrol (ULP) the problem went away. Cheers
 

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I would try all of the above. Sometimes you can't check a wire just by looking at it. Try replacing the spark plugs and wires if they havent been done in a long time. If none of the above does anything then you have to dig deeper. I would check the compression on that cycl compared to the rest. You should have 100 psi or better. If it is low, there is your problem. Note: a bad head gasket can cause low compression
 

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Had the same issue with my 01 Ford Ranger 6cy... 220K Stuttering like it had water in the fuel...or was cutting out (like you described).. was MUCH worse when it was damp and/or raining.... Happened twice and both times it was a spark plug wire. Couldn't see any cracks on the outer wire and the second time it happened was with the new set... after a couple months of being on. If you have a trusted mechanic available... he (or she) should have a tester to clip on the wires to check current flow.
 

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When light cruising or decelerating, the plugs need more voltage to fire - the cylinder's A/F charge is not near as much.

A bad plug wire - like jumping out of the insulation - will cause a quick "thump" misfire, but only on that cylinder. It would not cause it to shut off completely, even for a split second.

But - insulation breakdown in a coil wire or a bad coil kills all the cylinders.

Try this - use a spray bottle of windex, 409, water etc - something wet (not flammable.)
Spray it on the coil wire, cap, and the coil. If the insulation is leaking externally, it'll run bad or die when you hit the spot.

It still could be the coil leaking internally - they have a reputation for that. They aren't expensive (get a good one, not an Autozone Chinese knock-off) - plus keep the old one with you as an emergency spare.
 

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Thinking about it - remembering a simple trick.
Before throwing a coil at it - try this:
Engine off - Pull the coil wire out of the distributor cap. Have someone crank it while you hold the bare end of the coil wire close to ground.

Caution --- Use insulated pliers or a thick rag - if the spark jumps to you it'll knock you into the middle of next week!

You should be able to draw a crispy thin blue spark up to about 1/2" long - if the coil is good.

If it's shorter, yellow, red, or hisses at you like a snake - replace coil.

1/2" in free air is roughly 30,000 volts.
 

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Also a common problem for newer jeeps is the cps. Crankcase position sensor. Not sure how to check it, but have read about lots of guys with this problem.
 

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Discussion Starter · #17 ·
k well i screwed up with the code, was realy frusterated to i got a code reader. it said p0112 which is intake air temp sensore low voltage. how could that make my jeep be running so bad???
 

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Cause the sensor is giving the PCM a false reading making it thing that it either needs to richen or lean the air/fuel mixture to maintain the 14:1 ratio.
 
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