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MISFIRES, RANDOM

Discussion in 'Wrangler TJ (1996-2006)' started by gowenby2002, Mar 26, 2018.

  1. Mar 26, 2018 at 1:12 PM
    #1
    gowenby2002

    gowenby2002 [OP] Member

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    skips when run hard or high speed. goes into limp mode. switch off, restart and runs fine, but will repeat if ran hard or high speed. shows codes 300,301,302,303,304,305,306, which is misfire on respective cyl. and random misfires. Any ideas on this? or just start replacing ignition parts?
     
  2. Mar 26, 2018 at 2:41 PM
    #2
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine Moderator

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    Welcome to the site! I would check for any intake leaks, or cracks in vacuum lines.
     
    JKBob 25 likes this.
  3. Mar 26, 2018 at 6:19 PM
    #3
    gowenby2002

    gowenby2002 [OP] Member

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    Ok, thanks
     
  4. Mar 27, 2018 at 7:04 PM
    #4
    JKBob 25

    JKBob 25 Well-Known Member

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    Welcome to the forum @gowenby2002. You find a fix at this point? Sorry, no idea on codes. But there is a few members here that are great with codes. Have you narrowed them down? Again....welcome.
     
  5. Mar 28, 2018 at 7:43 AM
    #5
    mudbug85603

    mudbug85603 Active Member

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    Single-tipped platinum plugs like the Autolite AP985 or Champion 3034 can cause a bad idle or even misfires. you can run conventional plugs, double-tipped platinum plugs like the Autolite APP-985 or Champion 7034, or an iridium-tipped plug like the Autolite XP-985.
     
  6. Mar 28, 2018 at 8:55 AM
    #6
    Prerunner1982

    Prerunner1982 Well-Known Member

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    @gowenby2002 when was the last time a tune up was done?

    As far as plugs the Champion Copper 412 plugs are fine. Run them in all 3 of my 4.0 XJs with no issues.
     
    OFFGRID likes this.
  7. Mar 28, 2018 at 9:17 AM
    #7
    OFFGRID

    OFFGRID Well-Known Member

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    Agreed @Prerunner1982, Basic Autolite, Champion, or AC Delco copper plugs are the best for the 4.0 and 4.2.
     
  8. Mar 29, 2018 at 9:07 AM
    #8
    Offroad798

    Offroad798 Well-Known Member

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    Welcome to the site. When I worked for the dealers, and working on drive ability problems: if Gm products we would replace the spark plugs with AC delco plugs, Chrysler (jeep) we would pull plugs and replace with champion etc. This was a step we used to fix lean idle miss. This is an at idle and just off idle correction. There are lots of other thins to look at. Code P0300 is a code that is generated when your engine has a misfire that is not related to only one cylinder. 301 - 306 relates to the other cylinders. Barring no mechanical engine problem (high mileage). I would do a fuel test and or cylinder lead down. If mech bad or high mileage. Do This to check: Visual inspection first , 2) Fuel pressure (usually low) 3) Vacuum leak 4) EGR system. Secondary systems (Less common) Faulty coil 2) plugs and wires 3) cam or crank sensor 4) Ign module 5) computer Ive never seen this. If you have access to someone with a scanner or access to a scanner you can check alot of these systems and see this information in real time. This is just a quick things for you to check. Remember something is causing a misfire conde on all cylinders so its usually something that ties into everything. Example Vacuum leak, low fuel pressure would affect all cylinders where as a plug would affect one cylinder. Good luck -
     
    aggrex, Prerunner1982 and OFFGRID like this.
  9. Mar 29, 2018 at 9:18 AM
    #9
    OFFGRID

    OFFGRID Well-Known Member

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    Great Information @Offroad798. I wish there was a way I could file away the really good comments on here for later use. I foresee myself spending an hour looking for this post in the future.
     
    Last edited: Mar 29, 2018
  10. Mar 29, 2018 at 9:20 AM
    #10
    Offroad798

    Offroad798 Well-Known Member

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    I agree OFFGRID.
     
  11. Mar 29, 2018 at 4:06 PM
    #11
    gowenby2002

    gowenby2002 [OP] Member

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    O K Thanks to All. Sorry, I've not had time to check any thing yet, but will start there. Thanks again
     
  12. Apr 14, 2018 at 7:26 AM
    #12
    gowenby2002

    gowenby2002 [OP] Member

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    Thanks again to all, changed cam sensor, no difference. Dealer says to use NGK plugs, under hood sticker says Champion, went with sticker(champion), runs fine. thanks again.
     
    aggrex and Prerunner1982 like this.
  13. Apr 16, 2018 at 9:12 AM
    #13
    OFFGRID

    OFFGRID Well-Known Member

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    Howell fuel injection, header, HEI distributor, TH350, NP208, SOA lift with YJ springs in the front & GW springs in the Rear. AMC20 with G2 1 piece chromos trussed, Dana 30 with G2 chromos and 760x ujoints and MM Stainless Hubs, Geared 4.56. Tom Woods shafts, Metal cloaks, Caged, 37" Toyo MTs.
    Glad you fixed it. Its crazy how much spark plugs effect how well a jeep runs.
     
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