Thread: engine going crazy...computer problem?

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  1. #1 engine going crazy...computer problem? 
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    a few days ago I was driving the jeep and all of a sudden it started studdering and misfiring really bad and since I'm in college now I don't have much time to mess with it so I took it to a shop. The guy I took it to determined that the coil pack was bad so he replaced it. I forgot to mention that as soon as this started it also began taking a looong time to start, first just turning over and then slowly beginning to fire a little until it barely cranked. After the coil pack was replaced it seemed to not be misfiring nearly as much but it still takes a very long time to start and now it has started backfiring like crazy when the rpm's pick up.

    The shop that has it just called and basically said that they are not going to charge me for the parts since they didn't fix it and after working on it for two days they can't say for sure whats wrong with it but they speculate that the computer is bad and said I should take it to the dealership.

    Any suggestions on what might be going on would be appreciated. It was hard for me to even leave my baby in the hands of a mechanic across from my dorm and I hate stealerships.
    2000 WJ = rockcrawler
    4.0L
    IRO 3'' and 32'' bighorns
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  2. #2 Re: engine going crazy...computer problem? 
    Senior Member ATL ZJ's Avatar
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    what's your fuel pressure like and when was the last time you replaced your fuel filter?
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  3. #3 Re: engine going crazy...computer problem? 
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    i say its the CPS either crank or cam.

    anyone else think the same?
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  4. #4 Re: engine going crazy...computer problem? 
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    fuel filter is a couple months ago and he tested the fuel pressure and it was good. Crank position sensor is also a couple months old. We thew a new cam position sensor at it just in case but that didn't change anything
    2000 WJ = rockcrawler
    4.0L
    IRO 3'' and 32'' bighorns
    ford 9''
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  5. #5 Re: engine going crazy...computer problem? 
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    maybe one of the throttle body sensors?
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  6. #6 Re: engine going crazy...computer problem? 
    Senior Member it usually runs fine's Avatar
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    Any of the injectors have gas leaking out of them? Open the intake up and get some starting fluid, spray some in the intake then start it, see if it still takes a while. Also spray it again when the sputtering and bf starts. It sounds like fuel dlivery problem to me. Fuel pumps often die after changing out neglected filters FWIW. Are any of the fuel lines under the vehicle kinked, leaking etc? Look at your gas tank for wet spots.
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  7. #7 Re: engine going crazy...computer problem? 
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    None of that is leaking, i'm borrowing my buddies trailer to tow it back to my house tomorrow so hopefully I can play with it then. Would a fuel delivery issue cause backfiring? from what ive been told the pump either works or it doesn't.
    2000 WJ = rockcrawler
    4.0L
    IRO 3'' and 32'' bighorns
    ford 9''
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  8. #8 Re: engine going crazy...computer problem? 
    Senior Member it usually runs fine's Avatar
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    Wow thats a pearl of wisdom " Either it works or it doesn't" Well in that case I don't think your jeep is working. For what its worth my pump took two weeks to die( while doing similiar things that your jeep is doing) and my buddies was running one minute, then would not start the next. So I believe every pump dies differently.
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  9. #9 Re: engine going crazy...computer problem? 
    Senior Member ATL ZJ's Avatar
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    Quote Originally Posted by cowboy63b View Post
    i say its the CPS either crank or cam.

    anyone else think the same?
    No, 99 times out of 100, it will not run with a bad crank sensor.

    I have also had pumps bite the dust over a longer period of time.

    My .02 cents, you need to do less guessing and more testing
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  10. #10 Re: engine going crazy...computer problem? 
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    point taken.
    No longer a JeepTech01 fan.

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  11. #11 Re: engine going crazy...computer problem? 
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    Can you get any codes to show using the ignition key on/off/on/off/on method?.........if you can get somes codes up it may be a starting point.
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  12. #12 Re: engine going crazy...computer problem? 
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    Nope it is not putting out any codes. The shop that I took it to said that they checked the fuel pressure and it was "good". If I take the computer out is there anywhere that would be able to test it?
    2000 WJ = rockcrawler
    4.0L
    IRO 3'' and 32'' bighorns
    ford 9''
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  13. #13 Re: engine going crazy...computer problem? 
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    I can get another pcm from the junk yard from another 4.0 wj fairly cheap. Is there anything wrong with slapping another one in there and seeing if it fixes whats going on?
    2000 WJ = rockcrawler
    4.0L
    IRO 3'' and 32'' bighorns
    ford 9''
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