1jz missfire HELP PLEASE !!

Thread in 'Technical Questions' started by zombie, Jan 12, 2011.

  1. zombie

    zombie Active Member

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    Ok so had a missfire in the JZX90, but it has a vented carbon hood that was letting loads of water and crap get in around the plugs. So blew all the crap out and swapped the plugs to some new ones.

    pulled out some iridiums grade 8

    put in some ngk copper grade 7 ( as they were cheap and if that cured the missfire was gunna get some iridiums/platinums in there)

    Now the missfire is even worse, and no water has got in there since. Before it was intermittent and would hold boost back after about 4,500 rpm

    Now it sounds like a machine gun when boost is about to come on and won't boost at all.



    Coilpacks?

    ignitor amp box thingy?

    Are the grade 7 plugs not cold enough and the water was causing it in the firstplace, the brand new but crappy plugs are causing an entirely new missfire?

    help! This is all on stock boost by the way.
     
  2. Damien

    Damien ~London Folk~

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    as per my facenovel message you need to specify the missfire.

    on one cylinder? more? all?

    on boost? on idle?

    does it pop/backfire when you come on/ off the revs?
     
  3. zombie

    zombie Active Member

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    At a guess, all cylinders

    just on boost, idles fine and revs fine upto boost

    not that I could notice
     
  4. Jason

    Jason Nurse?

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    did you gap the plugs big man? thats the first thing i would do, the only thing you have changed is the plugs and its got worse... if gapping them doesnt work id clean the originals up and put them back in.. also check all the wires as you might have disturbed them when changing the plugs. Im not that up on Jz's (yet) but a common fault on RBs was the earth cable to the ignitor would deteriorate, and not earth propertly, causing intermittent missfire that was really hard to trace if you didnt know what you were looking for..

    So, check all the wires, check the earths, make new earths if your not 100% sure about any of em.... and good luck!
     
  5. zombie

    zombie Active Member

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    I literally just chucked the plugs in with the standard gap, worth closing the gap on them?

    and IDIOTICALLY I just left the plugs on the floor last night and it has rained cause I thought they were done with. Can't use them now surely?
     
  6. zombie

    zombie Active Member

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    P.s just checked on a few supra forums and they reckon the stock gap for a JZ is about .8

    Well I had read that 1.1 would be fine, and I can't be sure because I didn't have a gauge but they looked about 1mm at least!

    So worth gapping down to .8? Would it really make that much of a difference?
     
  7. Jason

    Jason Nurse?

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    yea man DEF would make a difference... dont think that any plug, no matter how expensive, is gapped properly from the factory... think about it, if the gap is larger than it should be then the spark is going to be blown out easier (due to the increased gap its gotta travel)... this will show up on boost obv..
    it might not cure it, its might be something else, but you gotta eliminate this before moving on and checking anything else :)
     
  8. milez

    milez Active Member

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    the bcpr7es are norm 7-9mm from exerperiance, Get them out and check them dude. WHat fuel system is it running? Map?
     
  9. zombie

    zombie Active Member

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    Damn, I was hoping they were something stupid like 1.3mm from the factory, will gap them down tomorrow anyway.

    HKS fuel pump man

    map as in the tune? then no stock ecu or you referring to map sensor?

    Logically it should either be the plugs or a vac line blown off somewhere so I have a boost leak. Or as Jason said, the coilpack wiring/earths.

    Actually the coils on this jz, the first 4 don't have the proper wiring plugs into them, just 2 little connectors pushed in, one even has a cable tie around it!
     
  10. Jebend

    Jebend Member

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    This may sound very stupid but check your intercooler & pipes, my skyline sounded like it had slipped a tooth one day, black smoking, shooting huge flames when on boost. Very nearly started to take the engine out before i noticed the bottom intercooler pipe clip had been knocked off (speed bumps at a guess) and was sucking air in. worth checking dude as it costs Fooook all :)
     
  11. zombie

    zombie Active Member

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    Will do man cheers
     
  12. dez 156

    dez 156 Member

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    check the plugs going onto the coilpacks for corrosion and the wires, i had a customers car with this problem, soldered on new plugs... problem solved
     
  13. David Reid

    David Reid RB30 Charger

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    Try closing the gap up until the miss fire goes away, I am sure Greg told me he goes down to .5 for high boost cars. If yours is running stanard boost there must be something else wrong but closing the gaps up could get you miss fire free while you work out what else is wrong.
     
  14. zombie

    zombie Active Member

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    Cheers man, to be honest, the gap on these plugs could just be wayyyyy to high anyway, so going to regap them to .8 tomorrow and see what happens!

    If not methodically go through everything else!
     
  15. Jme

    Jme Member

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    The joys of cars buddy. its all part of getting to know your Jz inside out.

    Clean up and dry your old plugs then gap them. You want the gapping tool to glide in the gap with a little friction. mine are .8

    As for your coil packs....just get new ones from toyota. sounds like there foooked. show the guy at toymotor you know what youre talking about and you mite get 10% off. Think they are £30 a pair?? Go in with your chassis number dude as they dont go off anything else.

    also get new conectors that clip into the coilpacks.

    The missfire may be worse cos youve cleaned all the crap out from around your plugs, almost like they were being insulated to a point, and now its all clean a failed coil has a nice clean head to jump.


    Try that.

    let no more water get down there.

    good luck mate.
     
  16. zombie

    zombie Active Member

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    Cheers mate, for some reason I thought jz coilpacks were like £300 like skyline ones.

    Will give them a call tomorrow.

    Although isn't it just worth gapping the new plugs rather than fucking around with the old ones?
     
  17. Jme

    Jme Member

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    Just start from the beginning for now buddy.

    try and pop in to toyota in person as they will only give you the price on the wromg itam
     
  18. David Reid

    David Reid RB30 Charger

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    Just remebered the terminals in the electrical connectors onto the coil packs also open up a give a slopy fit. Both Ryan of 2 bar tuning and Greg told me to close them up before refitting them every time the coilpacks are removed.
     
  19. zombie

    zombie Active Member

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    Well Ben (horne) has some spare coilpacks for me to try out which he is going to get in the post to me, so if it's that I can buy some but don't have to fork out for them if that's not the issue.

    Will regap the plugs tomorrow anyway.
     
  20. DR1FTER

    DR1FTER Active Member

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    happy to help buddy, lets hope its them ;)
     

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