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Thread: Misfire at cruising speeds

  1. #1
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    Misfire at cruising speeds

    2006 Ulysses
    Recently I went on a trip that was over 300 miles each way. On the way there, I had the bike misfire for a few seconds and I let off the gas and got back on it and I had no other issues that day. I chalked it up to bad gas.
    On the way back, it started doing it again, closer to the end of the trip. It would misfire, then I would let off until it stopped and throttle back up. It would be fine for a bit and then do it again.

    When I got back, I checked for intake leaks. Didn't find any. The seals, spark plugs, plug wires were all replaced over the winter.
    This was the first long trip I had been on this year.

    This past weekend, I took another trip, about 2 hours each way. On the way there, it only acted up once and on the way back, it acted up twice. Only if I was staying at a steady speed of 75-80 mph.
    If I was going slower, then I had no problems. and I don't think I had problems when I went faster.

    I have been reading up on the cam position sensor. I am not seeing the tach drop to 0 like some people reported, but I did read similar issues to what I am seeing.
    AVF is showing 110 and the only codes are 13 and 21 for AEV. I need to replace the cable because it isn't opening and closing properly.
    I have had trouble connecting to the buelltooth when the bike is running, so I can't tell what it reads when the misfire occurs (engine light flashes).

    Thoughts?
    Last edited by spigatelli; 09-07-2021 at 04:36 PM.

  2. #2
    Senior Member Barrett's Avatar
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    Sir: My thoughts? I would start with the below.

    1-Intermittent "misfire" in conjunction with simultaneous momentary CEL is always a sign that your ECM just saw something it didn't like. This is always either a 12V power interruption...or ground interruption. Check all grounds including rear sub-frame to main-frame connections closely for corrosion and loose connections. Check ECM ground closely as well.
    2-Check and clean and tighten all 4 battery cable connections and battery terminals. A problem on 1 or more of them will cause your precise problem.
    3-random FC's 13&21 almost always a result of faulty ground. See #1 above.
    4-The CPS plug on your year XB is behind the plastic front pulley cover. Remove same, separate all connectors, clean, inspect, reconnect.
    5-Remove Key Switch relay and check for corrosion...loose or broken fusebox terminals...clean...reinstall.
    6-A sudden loss of power and lackluster throttle response "at speed" is almost always associated with an Interactive Exhaust Valve System failing actuator assembly and/or cable/muffler valve failing.

  3. #3
    Senior Member 34nineteen's Avatar
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    Great advice as always! This man is badass and legend. Clints pretty cool too.

  4. #4
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    Quote Originally Posted by Barrett View Post
    Sir: My thoughts? I would start with the below.

    1-Intermittent "misfire" in conjunction with simultaneous momentary CEL is always a sign that your ECM just saw something it didn't like. This is always either a 12V power interruption...or ground interruption. Check all grounds including rear sub-frame to main-frame connections closely for corrosion and loose connections. Check ECM ground closely as well.
    2-Check and clean and tighten all 4 battery cable connections and battery terminals. A problem on 1 or more of them will cause your precise problem.
    3-random FC's 13&21 almost always a result of faulty ground. See #1 above.
    4-The CPS plug on your year XB is behind the plastic front pulley cover. Remove same, separate all connectors, clean, inspect, reconnect.
    5-Remove Key Switch relay and check for corrosion...loose or broken fusebox terminals...clean...reinstall.
    6-A sudden loss of power and lackluster throttle response "at speed" is almost always associated with an Interactive Exhaust Valve System failing actuator assembly and/or cable/muffler valve failing.
    Thanks for the tips. I have been cleaning grounds and I cleaned the connection for the CPS.
    Cleaned all of the battery connections.
    This evening, I'll jump into the key switch relay and double check the fuse box terminals.
    Biggest problem now is that I have to take it for a long freeway ride to test it, which means going for a longer ride to get to open freeway. So it goes...

  5. #5
    Senior Member Cooter's Avatar
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    The CPS commonly fails with temperature. An easier test method is to heat it with a hairdryer or carefully with a heat gun while idling, instead of the long drive away from tools.

    Barrett is correct (as usual) with the checks to perform and the ignition primary circuit being compromised will absolutely cause an engine to cut out. Commonly, cutting out could be the key switch or red run switch being corroded, and thats happening more often because they are exposed to the elements and these are getting older. A wiggle test should expose either of those switches as the culprit, but cleaning them (CRC Electronics cleaner) is never a bad idea.

    If it is indeed more of a "mis-fire" like you describe, I would still focus on the the ignition, including the secondary circuit.
    CPS gives the TDC signal to the ECM, ECM times and then outputs that single signal to both cylinders, via the coil primary wires, then the coil ups the voltage from each of those signals separately and sends it to the plugs.
    Check:
    CPS, supply voltage, ground path, and signal wire to the ECM.
    ECM primary wires to each side of the coil
    Coil, supply voltage, ground path.
    Spark plug wires and boots.

    If you have access to ECMDroid using a Bluetooth dongle (I love my Buelltooth from Rev-Mo.com) I would check the AFV/ EGO and that should immediately show any issues with intake leaks or failing fuel pumps.

  6. #6
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    Both AFV and EGO are at 110%

  7. #7
    Senior Member Cooter's Avatar
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    Which means ECM is currently compensating slightly rich, but well within normal parameters. Not a lean mis-fire IMO.

  8. #8
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    I got in there to clean up the grounds under the airbox and I found a bare spot on the head temp sensor wire. Hopefully, that was the issue.



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