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Thread: 2003 XB9S: engine misfire/cut out problem

  1. #1
    Hi guys,
    Long time lurker, first time poster. Hoping to get some help on my XB. Tried to get some help on badweather but got nowhere so now I'm trying here.

    Okay, here's what's up. I ride my bike 120 miles per day Monday thru Friday. About a year ago, I got a random misfire while riding home. 99% of the time it only misfires/cuts once and when it does the CEL comes on for about 3-5 seconds and then it turns off and everything goes back to normal. It did this twice everyday (once coming to work and once going home) for many months and it wasn't a big deal. Then one time it did it once, then again, and again and again and again. This time it wasn't just cutting out, it was fully back firing. It did it for about 5 minutes straight (seemed like an eternity while I was trying to split lanes in rush hour LA traffic with a bike that wouldn't run right) and then it stopped and was fine again.

    So, sometimes it'll just cut out and other times it'll backfire and everytime the CEL comes on and then immediately goes out. The one time it did it for 5 minutes straight I noticed that the tach would drop to zero when it misfired... hmmm a clue maybe? The other thing is that there are no stored codes. I say again... NO STORED CODES!

    About 90% of the time the misfire/cute would happen in almost the exact same part of my commute (in Long Beach for those that want to know) which was 25-35 minutes into my trip. So it seems time based which is actually more likely to be a temp issue. Yes, my fan still works and always turns on when it's supposed to and no my bike doesn't seem to be running hot. The only mods are a K&N filter (stock air box) and a Special OPS muffler.

    It's been doing this misfire/cut maddness for a year now. Like I said, it usually only does it once and then it's fine but today it did it like 10 times and it's always at the worst times.

    Is it possible that I have a bad temp sensor and the ECU is going into "fire every other cylinder" mode? Has anyone else experienced this? Any insight? Any help would be greatly appreciated. I really depend on my XB and I need it to be safe and dependable.



  2. #2
    Uh oh, kinda quiet. Decided to pull the air box off and front sprocket cover off and check things out tonight. Everything looks fine. Nothing worn through, nothing broken, nothing wrong as far as I can tell. Did a wiggle test while idling and nothing happened. Going to stop by the stealership tomorrow and order up the engine temp sensor and start there. I thought about replacing the coil, plug wires, and spark plugs but honestly they look fine. I did the plugs 20k ago and will need to do them by the end of the year but they're fine for now.

  3. #3
    Senior Member
    Join Date
    Oct 2011
    You can do a datalog and track the temp to see if it fluctuates other than it should. Also you can use a multimeter to test the temp sensor, I'd start checking and testing things before you buy something unessesary.

  4. #4
    Senior Member
    Join Date
    Jun 2011
    If you have ECMspy since the CEL is coming on it will store the trouble code then look in the book and it will tell you roughly what's going on that's a good way to start. If you don't have a cable and can't hook up to ECMspy then you could see if anyone lives close to you who has that stuff to look it up.

    If you go to the stealership you could see if they would be willing to pull the code for you. It usually costs ya though.

    I'm on my mobile right now I know there are a few more pages on trouble shooting without ECMspy but I'll look for them in a few hours when I'm out of work.

  5. #5
    Senior Member
    Join Date
    Jun 2011
    Also, welcome to the forums!

    Ok so here are some pages for you:

    How to check CEL without ECMspy Here
    Possible ECM codes Here: I would check your manual if you have one though. Im not sure if they changed from year to year.

    Also, here is a great page for you its where I started to gather a lot of information and look for stuff often Here

  6. #6
    Also you can use a multimeter to test the temp sensor
    Good point. When thermistor or RTD type sensors go bad, they're usually bad and stay bad. This random inconsistency honestly doesn't sound like a bad temp sensor that's gone bad and is bad all the time. This sounds like an intermittent issue.

    since the CEL is coming on it will store the trouble code
    That's the problem, the CEL only comes on for a sec and no DTCs are being stored. I've only ever had one code EVER while I've owned this bike and it was for the fan when it went out. Honestly I think that's a problem with this early generation EFI system is that the diagnostic functionality is actually very limited and whatever is happening isn't something specific enough to throw a code.

    Like I mentioned in my second post, I pulled off the air box and front sprocket cover and checked out all the wiring. I can see where vibe has had a real impact on the wiring with things being rubbed kinda thin in some spots but I have no breaks, no shorts, no frays, or anything else that could visibly be causing this problem.

  7. #7
    Still doing it and no CELs. Any thoughts? What's the possibility of it being the cam sensor?

  8. #8
    Senior Member
    Join Date
    Aug 2009
    03-07 have possible faulty regulators (symptoms include low battery; cel; lights/tach/speedo dimming or dropping)

    CKP crank pos sensor; known to have faults, can cause misfire/idling/sputter problems

    CMP cam pos sensor; faulty time to time, can cause misfire/idling/sputter/low rpm problems

    Intake Manifold; loose bolts can cause minor/major leaks, wreaks havoc on the IAC,IAT sensors

  9. #9
    Well, FWIW, I have zero idling or low rpm issues and zero battery issues as well. My bike runs PERFECT 99% of the time. It's just this stupid misfire thing... and it almost always does it in the same exact spot during my commute. After about 30 minutes it'll misfire... except that the weird thing is is that it actually didn't do it yesterday going to work but it did it twice coming home. The day before it did it four times going to work but it didn't start until I had been riding for 30 minutes.

    I had originally thought it was temp related but I would think that the engine would have already been at operating temp if I've been riding it pretty hard on the freeway. It's not like it just keeps getting hotter and hotter and hotter forever. It eventually peaks out and equalizes. So may it's not a temp issue. Maybe the ECUs bad or has some kind of problem.

    Someone mentioned logging... how would I be able to do logger if it means riding the bike for at least 30 minutes before it'll misfire? Can you do "internal" logging with the stock ECU or can you only do "external" logs with a PC?

  10. #10
    Senior Member
    Join Date
    May 2012
    Have you tryed the 12V relays? I have had very similar things like this happen to me. It was the 12V relays in my case.

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