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Thread: WJ 4.7 issues...

  1. #1
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    WJ 4.7 issues...

    hey everyone,
    i have a 99 WJ that feels like is is running on 2 cylinders... coil packs all test good for continuity and plugs all have power to them but looks like some plugs are not firing (all 8 are brand new)
    heads are good, gaskets are good, new rod and main bearings just put in...
    any ideas as to why it is all of a sudden running like crap??

    any help would be GREATLY appreciated!!
    thanks

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    Did you do a Compression Check...

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    heading out to do that now...

  4. #4
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    Could also be a crank position sensor as it would possibly not tell the computer proper times to fire the plugs. i know mine was starting and running kinda crappy until I changed it and runs great now. This is assuming it is mechanically good to go.

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    Swap the coils. From the ones that are firing with one that isnt.

    Quick easy test to do.

    4.7s and 3.87s eat coils for breakfast.

  6. #6
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    just did a compression test... who wants to come help me push thing into the lake out back??
    just plained the heads to make sure they were not warped since when i bought it, it had a blown gasket. full top end gasket kit put in...
    not sure i have the patience or time for tearing this thing down to find out the issue

  7. #7
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    so whats the result of the comp test
    rockin the 95 xj custom 4inch lift and 285/75/16 bfg mud terrain km2 and bds discos R.I.P

    98 xj 4.0L 5spd 4.5" zone lift and m/t sidebiters looking for 33s

  8. #8
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    was between 125 and 140.... except for the second cylinder back on the passenger side.

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    is there any tracing or coolent on the plug for that cylender

  10. #10
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    just black from not firing it looks like.

  11. #11
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    what was the comp of that cylander

  12. #12
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    a big fat ZERO :-/

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    thats wierd there should be at lest somthing
    i would pull the head

  14. #14
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    took the valve cover off today... busted valve spring... FACK!!
    anyone have any luck removing the springs without removing the head?
    anyone want a case of beer to fix it while i stand behind/drink a beer and cheer you on?? lol

  15. #15
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    make sur the valves are close fill the cylander with air pressure and get an oncar valve spring installer

    like this http://shop.advanceautoparts.com/web...21-177716954-2
    Last edited by blown85xj; 11-11-2011 at 02:34 PM.

  16. #16
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    thanks for the info blown85xj! no bite on the install for beer though, eh?? haha

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    4.7 are a finniky motor! had one started to trow timming codes then it blew a gasket found a used on and it whent 3 moths! sold it and bought a 99 with a 4.0 in it year and a half ago the motor is now got a bad rod knock.... stroker time!

  18. #18
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    Well, fixed the valve spring. Up and running again!
    Has a rough idle but no codes... Any ideas??

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