Misfire

Discussion in 'KJ General Discussion' started by VooDoo, Apr 11, 2011.

  1. VooDoo

    VooDoo New Member

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    Check light comes on every 200 miles or so. Always clylinder 5. I have tried new plugs, and coil. Runs great otherwise. Anyone think it might be a injector or a ecu glitch? Input please.
     
  2. VooDoo

    VooDoo New Member

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    Anyone?
     
  3. Minimike

    Minimike Full Access Member

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    If its not spark, the it has to be fuel or mechanical issue (bad valve). Using a mechanic stethoscope listen to the injector on cylinder #5, or use a large long screw driver. You should hear a relatively loud clicking noise. This means its opening and closing. Even if it sounds good it may be clogged. A good way to diagnose a bad injector is to swap an injector with another cylinder and see if the misfire follows. If the injector is fine you may have engine damage. And always as a cheap maintenance item make sure to clean your intake sensors.
     
  4. 05kj6spd

    05kj6spd Full Access Member

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    Try moving your injector like posted above. It it's starting to leak fuel in to the cylinder it will keep fouling plugs. Look at the next plug you pull. Changing the plug may fix it temp but if it's bad injector it may just take a while to foul the next plug.
     
  5. Minimike

    Minimike Full Access Member

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    well VooDoo any luck with diagnosis? If you can tell me what you have done I can help guide you along.
     
  6. ridenby

    ridenby Gold Supporter

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    What are the codes it is showing?
     
  7. VooDoo

    VooDoo New Member

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    new coil and new plugs always cyl 5 misfire every 100-200 miles. Iam going to swap injectors and see what happens. if it is the injector great i will buy a whole set. if not it is for sale.
     
  8. Minimike

    Minimike Full Access Member

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    that's too bad. I do hope you will either trade it into a dealership so they can fix it or let the potential owner know about the issue. It sucks when you buy a vehicle only to find out it was a major problem.
     
  9. Dmut

    Dmut Full Access Member

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    could be a wiring to coil 5
     
  10. VooDoo

    VooDoo New Member

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    wiring looks good. anyone have instruction for injector replacement i got a new one today and want to get this straight
     
  11. ridenby

    ridenby Gold Supporter

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    What is the code? If it is an injector it will have a code saying so,same for coil prob.
     
  12. VooDoo

    VooDoo New Member

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    it just says #5 misfire
     
  13. ridenby

    ridenby Gold Supporter

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    It will be P---- something. How are you arriving at this information?
     
  14. 05kj6spd

    05kj6spd Full Access Member

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    It would be a P0305 code. That's the OBD II code for a cylinder 5 misfire. It can be caused by one of the following....a bad spark plug, a bad coil, a bad injector, a burnt exhaust valve, a bad catalytic convertor, a bad O2 sensor. The first thing to check is the spark...pull the plug, if it's fouled by gas clean it and test to see if the plug is does indeed spark. In this case he replaced the spark plug with a good one. Next check the coil, use an OHM meter, if it's in spec it should be good. Once again he has already replaced that. Next check the injector, a noid light will tell if the wiring is working but a common check is to remove the injector from the affected cylinder and move it to another location (keep track of where you put it) clear the codes and drive until the problem repeats. If the problem repeats at the new cylinder (why you keep track) then the injector is probably leaking. If none of the above pan out you maybe have to drop the exhaust or try and take a peek inside the motor some way. Most vehicles will not throw a code for a coil if it's out of spec and the spark is just weak, and they won't give a code for an injector that is dripping unatomized fuel into the engine. Those codes only appear when there is a problem with the wiring that the computer can detect. It has no why of check for a mechanical problem with the injector or the OHMS of the coil.
     
  15. VooDoo

    VooDoo New Member

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    changed the injector was really easy we will see what happens in the next few days
     
  16. tjkj2002

    tjkj2002 Full Access Member

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    A bad O2 sensor or bad cat will not cause a misfire on just one cylinder.There are far easier ways to test a misfire without any tools.
     
  17. Ry' N Jen

    Ry' N Jen Banned

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    I just had a P0304-CYLINDER NO.4 MISFIRE CEL come up last week...
    I installed six new spark plugs.
    Problem solved!
    BTW, what spark plugs did you use?
     
  18. 05kj6spd

    05kj6spd Full Access Member

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    Those are probably the least likely....especially for just one cylinder but that is what the FSM says to check. As far as testing a misfire without tools...you may be able to put your hands on the hood and feel the cars pain but in the real world we work with wrenches. You tell me great one how you fix all this with out getting your hands dirty. I gave the guy some info on what to check and how to do it and you gave squat. Just because you have a big KJ doesn't make you the expert on everything (just thought you should hear that) so instead of telling everyone that what the posted is in correct why not share your seeming endless knowledge with the rest of us.
     
  19. Banditsteve

    Banditsteve Full Access Member

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    X2. If the fault returns to same cyl, you could try moving coil pack and see if the fault moves with that. If the fault then returns to same cyl try moving plug. Its just a case of moving what you can one thing at a time and eliminating what it can be. Just because something is new it doesn't guarantee its 100%. When you have moved everything you can that is moveable, if the fault remains on no.5 cyl it is an internal issue. Good luck with the injector. :smokin:
     
  20. VooDoo

    VooDoo New Member

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    champion platinum