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Thread: Misfiring Issue

  1. #1
    JFizzleJR's Avatar
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    Misfiring Issue

    Hey guys, I need some help. My 2005 RXP isn't firing in cylinder #1 (rear cylinder). Changed the plugs, ran through gas, swapped ignition coils, checked the fuse in the MPEM...There's an extremely noticeable miss around 4500-4900 RPMs every time it hovers around that range. It tops out at 7000 RPMs and about 55 MPH. It's not an issue with the supercharger. The spark plug in that cylinder is always dry and clean. The injector is firing properly. Compression is 125-130 accross the board. I now have a Walbro high flow fuel pump with clean filters. I am going to do a leakdown test and then I'm out of ideas. Is there any chance this thing is stuck in a limp mode? No fault codes or anything. The only thing I can think of is the exhaust valves burned from running lean, but I'm not sure why the #1 cylinder is the only one noticeably affected. It's gotten progressively worse, but isn't running lean any longer. Any input would be greatly appreciated. My guess is the head will be coming off for valve work. All because of the weak stock fuel pump


  2. #2
    King_Of_Fun's Avatar
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    If the compression is 125-130 across the board, then the rings/valves should not be a concern. When you said "swapped ignition coils", I assume you meant swapped all 3 coils, one at a time, with a known good coil... Ron

  3. #3
    JFizzleJR's Avatar
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    Swapped all 3 with another set. And this is the second set of spark plugs -- still showing the same symptoms. Even moved the plugs from cylinder to cylinder. The dry/clean one started to fire when placed in a different cylinder, so it's not the plugs. Cyl. #1 is the problem...And it takes more revolutions to crank #1 to full psi on the compression test. It actually quits turning before the start button is let go. Almost like it overpowers the battery.. If that makes any sense.

  4. #4
    JFizzleJR's Avatar
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    Any ideas why a ski would run on 2 cylinders when compression is fine and spark/coils are working?

  5. #5
    JFizzleJR's Avatar
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    Anyone?

  6. #6
    Richieb's Avatar
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    Thinkin....

    Change the plugs.

  7. #7
    Golden Jet red fox's Avatar
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    Check The harness ,,,,

  8. #8
    iron head's Avatar
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    changes inj bad inj

  9. #9
    Richieb's Avatar
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    Quote Originally Posted by red fox View Post
    Check The harness ,,,,
    +1, Good point, plus connectors are not crapped-up.

  10. #10
    Moderator RX951's Avatar
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    I agree ,check all the connectors and your grounds. I hear a bad or weak ground causes weird stuff to happen

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