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Thread: XB misfire at constant RPM cruising (~3500 RPM).

  1. #1
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    XB misfire at constant RPM cruising (~3500 RPM).

    This is solved now but it took me 3 years and $2,500 before I finally got it right. Figured after all that, I should share the knowledge in case someone else is having the same issue.

    Note to the site admin. You may move / reuse / edit / whatever you like. Figured that this was worth others knowing.

    For 3 years I have been fighting the same frustrating issue with this bike. It runs well around town but will randomly start misfiring at interstate speed while cruising. Cutting the throttle OR going to WOT returns the bike to normal mode for a minute or so and then it starts misfiring again. Issue occurs between 3300 and 3700 rpm. I got a lot of good advice from the forums on where to look but this one seems to have stumped everyone.

    Well I finally solved this issue and from what I read, there are a bunch of other users with the same general issue that cannot find a resolution. I feel confident that I got the issue fixed this time as I have gone 3 months and 1,000 miles with no issue. So to save others the time and money, here is the history, hypotheses, and fix. It is a bit of a tale but read it so you know what DOES NOT work.

    When this started (2016) I would occasionally (not always) get the following codes:
    13 Oxygen sensor
    15 Intake air temperature sensor
    14 Engine temperature sensor
    16 Battery voltage
    21 inter active muffler control
    36 fan voltage

    I installed new battery, O2 sensor, air temp sensor in 2016. Bike worked for 1 week then issue returned. Near winter so I parked the bike.

    In 2017 I tested the fuel system and it seemed that fuel was being delivered properly so I guessed that the issue was electrical. Installed new plugs, wires, coil. Did a full test on the charging system (generator and regulator) and they passed. Replaced regulator anyway as it had surface damage (rock strike I think). Bike worked for 2 days then back to the same crap.

    A few completely useless dealer services resulted in new plugs (again) and a re-flash of the computer (and a lot of $).

    Did a complete wiring harness test (puled all the connectors, checked all the wires, checked the computer connections, .). Found a few small items but nothing that fixed the issue. It occurred to me that the exhaust valve opens and closes at this rpm range and the muffler was rusted (35,000 miles). So I disconnected the exhaust cable and jammed the valve open. Exhaust servo was free to rotate. No effect same problem. But I could not rule out an issue with the exhaust servo itself.

    Contacted KD Fab and got a drummer muffler (NO STUPID VALVES) and an IDS computer to match. KD was really helpful with good quality work. I knew I had this fixed now with a new muffler, computer and no servo. WRONG. Bike worked great for 2 days and then the misfire issue started all over again. But now the only errors were:

    13 Oxygen sensor
    15 Intake air temperature sensor
    14 Engine temperature sensor

    During 2017, I had noticed that my oil level was growing slowly during all of this so I thought that maybe the pressure regulator was pumping gas into the oil and (maybe) not supplying the injectors properly. The bike had 35,000 miles so it was probably due for a pump. It also seemed possible that I had an intake air leak that was vibration dependent or the TPS was shaking at the right frequency. Remember, this only occurred between 3300 and 3700 rpm. So I had a new fuel pump, regulator, throttle body (with new injectors, TPS, and seals), new plugs, and a new O2 installed. The plugs and O2 were in case the misfiring had fouled the last set. Bike worked great for 1 week then the same problem again.

    At this point I was considering the bike for scrap metal. $2,500+ in parts with no success. That said, all the parts I replaced were worn after so many miles and it was not irrational to replace them. Plus I knew a few were bad (fuel pressure, the first O2, .). But what could possibly be wrong with this thing?

    I went back to electrical (through shear process of elimination!) and thought about the errors, all three were from sensors on the same section of wiring harness. The O2 and engine temp are also single wire (duplexed signal) so any loss in battery voltage / circuit conductivity would cause them to appear failed. I clipped the sensors out of the wiring harness and built a new harness for these sensors that then spliced into the connectors at the computer. The original wires were taped at both ends. I knew I had to have the issue now. I had all new parts and new wiring to the sensors that were throwing codes. Test rode the bike and .. FAIL!!!! Same issue again.

    More thinking and screaming at the bike led me to suspect that there might be a ground issue. I had already checked this multiple times but I did again. No loose grounds. But what if the computer was not grounding well where I could not check? This was obviously a vibration issue where something was shaking. So I figured adding an extra ground would not hurt anything. I spliced into the black wire at the computer terminal (that is the ground wire for the electrical system). I made a connector for the splice and bolted it to the negative battery post. Now the harness was definitely grounded. AMAZINGLY - PROBLEM SOLVED.

    It has been 3 months and 1000 miles trouble free. No, the bike has not burned down. No, the bike has not blown fuses. No, the bike has not fried the IDS computer. All seems well. So the hypothesis is that the computer itself is losing grounding when shaking (do not have an explanation for where / how). Now I do not fault the computer as TWO computers have been tried without success . Remember that I ohm tested all the grounds to the computer while shaking the harness 2 years ago and again this year. I never found a loose ground or a break in the wiring that would affect this (did have to re-wire the head lights as a separate issue). I also added a foam stopper on top of the battery to keep the seat off the computer connectors in 2016. As best I can tell, this is an issue with how the computer is grounded / seated.

    If anyone has an alternate hypothesis, please add it. But I can tell you that multiple people have gone through this bike and not found the root cause (including me). Adding a ground to the wiring harness at the terminal (total of $0.12 in materials) solved what $2,500 had not. So, if you are one of the poor souls with a cruising speed misfire that cannot be eradicated, just try adding an additional ground to the computer. It cannot hurt anything.

    Side note: I do believe that the stupid exhaust valve and servo (thank you California pass by noise) were an issue. I suspect that some of the codes I was pulling were real servo codes that just happened to pop up during a ride that the ground fault occurred.

    Parts:
    O2 sensor 3 replacements
    Air temp sensor
    Engine temp sensor
    Battery 3 replacements
    Ignition coil
    Plug wires
    Pugs 3 sets
    Muffler
    IDS computer
    Throttle body
    TPS sensor
    Fuel pump
    Fuel regulator
    Fuel injectors

  2. #2
    Senior Member Cooter's Avatar
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    Glad you finally guessed correctly and found the issue to get you back on the road!

    Keep riding

  3. #3
    Hi
    I've just posted a whole lot on fixing earthing problems wrt chasing a midrange misfire, but there's one thing I didn't include in that 'novel'.
    I found that the lug that both wires from the ECM is crimped to, has a high resistance (like 7ohms when it should be nearly zero), and 0.7ohms is the upper limit if you don't want it to throw random earth voltage fluctuations
    I didn't mention it because I pretty much cured my problem with the massive earth return cable and the high resistance joint didn't seem to be part of my misfire problem. However if your crimped joint is changing in resistance through road shock or engine vibration or some other stress, then that will set your ECM to trying to compensate for what it thinks are valid voltage changes from your Engine Temp and O2 sensors, which are in that earth return loop.
    When I put a DMM across the lug and each of the earth pins in the black plug that plugs into the ECM both read the same 7 Ohms but when put across the 2 pins in the plug itself it showed near enough zero, i.e. the high resistance is in the crimp. You can maybe prove the same on your loom.
    I'm about to replace that crimped lug since it shouldn't be that high even if it doesn't affect the bike (yet). I'm half expecting that when I replace the the lug that the bike will spit and fart until it relearns what normal is. I'm going to change just one thing at a time to see what it does. - jv

    Edit: I originally found the high resistance crimp with my $10 DMM (measured 4 Ohms). I wondered if I'd measured right or it was accurate enough, so borrowed a $1000 Fluke DMM. Result was even higher resistance (the 7 Ohm above). After reassembling with CRC2.26, I measured over a period of weeks with the cheap DMM and kept getting lower (but not near-zero) resistances each time I measured, so got an electrician with a Fluke meter to measure again and now the resistance of the crimp is the same as touching the probes together (0.1 Ohm - where it should be). The high resistance didn't ever seem to be part of my misfire problem, though you'd expect it to be an issue. Poor original measuring or bad crimp fixed by CRC 2.26 'improv(ing) the electrical properties' - who knows? I won't be changing the crimped lug - just yet. Probably Konarider's got the better explanation below - jv
    Last edited by John Vreede; 07-30-2018 at 09:07 AM. Reason: more info/rethink

  4. #4
    Member herwawan's Avatar
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    That is a crazy story! Glad you eventually found the source of the issue and Im impressed by your focus and determination at fixing it. Lots of respect for that 🙌 thank you for sharing

  5. #5
    Senior Member konarider94's Avatar
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    Was this on a lightning model? The ground for the battery cable connects to one seat rail and the ecm grounds to the opposite one IIRC. Ive seen people repaint or powdercoat the seat rails(or subframe if you want to call it that) and then it doesn't ground to the frame properly where it bolts together. Or the little boss of material for the ecm ground ive seen covered in powdercoat which caused similar issues.

    I wonder if you were to take a look at the contact between the seat rails and frame if you would find anything useful. Sounds like the battery side has a better contact than the ecm side.

    If you have a firebolt then I'm not sure what the ground path is like.

  6. #6
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    Thanks for the info John. Never thought to ohm out a crimp! That may very well be the root here and I just bypassed it with a new ground.......

    Thanks konarider94. I did check the ground connections for cleanliness and tightness. They were good. Bike has not been repainted / etc. I do not believe that either ground has ever been loosened. Not to say that one might have an issue though. I did continuity tests on everything and it checked out. But I did not ohm the grounds as John noted. Should have done that.....

    But now I have a true ground and all is well. Documented all of this as it was so bizarre and 6 different people (including me) could not isolate the issue. Fix was super cheap and took 10 minutes with no down side that I can think of (other than I do not have a pristine harness now). So if anyone ever reports anything similar, add a ground to the system just to check.

    thanks everyone

  7. #7
    Senior Member GregoXB's Avatar
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    Can you snap a pic of the repair and tell us what year and model your motorcycle is?

  8. #8
    Senior Member lunaticfringe's Avatar
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    these XB's are notoriously hell on batteries and grounding points. been preaching that on here for what....10 years now????this is a brilliant thread and again...it all reverted back to those nasty ground gremlins around the battery box and sub-frame areas. moral to this story like most others on here is: 90% of XB problems are electrical and out of that percentage 90% of them are loose connections, corrosion, grounds gone astray. never forget that the majority of the things that the ecm accomplishes and is designed for is grounding. that is what triggers the coil, the fuel pump, cooling fan, various sensors, and the ecm itself. thanks for posting this up. it's brilliant!
    Last edited by lunaticfringe; 07-31-2018 at 01:47 PM.

  9. #9
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    Wow....
    Yep, Im in the same boat. I got my XB12S in 16...low miles (9k) ran rough. CE lights & stutters. I went thru several things and couldnt figure out anything, kept plugging away at this and that. No improvement, got fed up & mothballed it for most of 17/18.
    Back to resurrecting this XB!
    I know my battery is beat, so Ive ordered a new one & am gonna clean my grounds and try this re-grounding tip.
    Thnx for posting!!

  10. #10
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    Wow, nice write up! I had been having similar issues on my '08 12s. Was getting rear o2 inactive codes after stutter/misfire, so I just ran it open loop which fixed all of the stutter/misfire at 3500 rpm cruising. I do, however, still see stutter/misfire after running it high rpm and up towards 100 mph, so I'm guessing there is a ground issue somewhere caused by vibration. Will try this fix, thanks!



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