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Thread: '09 XB12scg has trouble idling, CEL codes

  1. #1

    Question '09 XB12scg has trouble idling, CEL codes

    Hello everyone

    I bought a used 2009 Buell XB12scg about 2 months ago. The bike is fantastic, and only has about 2700 miles on it. However, I have a couple problems with it. The bike has some trouble idling. When it’s cold, it’s mostly not a problem. However, when the bike gets hot (heavy traffic, city riding after pushing it on the highway) or I turn it off and then try to turn it back on again after a couple minutes, the bike fails to idle. It hesitates, pops, backfires (and sometimes misfires), and then dies. Under load, the bike has no problems at all. Above 2500rpm, it will pull and drive happily.

    That being said, if I start the bike cold, it will idle forever, with the fan coming on repeatedly to cool the sitting engine down. As of this morning, the bike's CEL light comes on and stays on at bike startup, which is new.

    Things I’ve done to diagnose it:

    • Changed spark plugs
    • Checked to see that the fan is running (runs over 15mph, runs when engine is too hot, runs after bike shut down when engine is hot)
    • Used a high-cfm house fan to cool off the left side of the bike after turn-off (bike is able to fire and idle after about 30 minutes of the fan on it, vs 1-2 hours normally)
    • Added StarTron to the fuel (Premium 93 octane)
    • Reset TPS
    • Checked CEL codes (using the ECM jumper method)


    The ECM has 4 CEL codes:

    • 13 - Oxygen sensor
    • 15 - Intake air temperature sensor
    • 21 - Interactive muffler control
    • 34 - Idle air controller


    I don't know if one or more of these CEL issues are causing the rest of the issues. I'm kind of at a loss for where to go from here. Could the IAC failure be causing an O2 sensor failure? Could the IAT sensor be causing the IAC issue? Would the IMC issue be caused by all the spitting and back/misfiring? Am I going to have to replace all of these things?

    If you have any other experience with this kind of issue, I’d love some advice. I love the bike but I need it to idle reliably before I get caught in a tunnel at rush hour (again).

    Thanks!

  2. #2
    I spent the day working on diagnosing further.

    I disassembled the air box and completely removed everything so I could access the IAC. I cleaned it and the opening it is inserted into with carb cleaner (wasn't that dirty). I also turned a bottle of air in a can upside down and used it to cool the sensor when it was hot and the bike was failing to idle. It improved it temporarily but went back to failing quickly thereafter.

    I removed the IATS and hit both the exposed part and body of the part with the compressed air. It made no difference.

    The IMC cable slides smoothly. I was able to actuate it by hand but I did not observe it moving when I twisted the throttle in neutral on the stand.

    The bike makes this whistling sound when it starts to stumble, like an asthmatic trying to grab for a breath. I took a video of it but won't be able to upload it until later.

  3. #3
    Senior Member AZmidget91's Avatar
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    Intake seals are leaking. What is the AFV?

  4. #4
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    hey cole: had something similar last year here. when in open loop like his situation the idle was erratic and a tad to high. ended up being the IAC unit and the base-plate to TB rubber air horn not being properly installed.

    The IMC cable slides smoothly. I was able to actuate it by hand but I did not observe it moving when I twisted the throttle in neutral on the stand.

    it won't under that circumstance.

  5. #5
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    Perform intake seals leakage test.

  6. #6
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    Well here is my crazy thought for the day! I do believe, almost positive, this happens. Imagine on a commute in the middle of a very hot day in Texas. Sitting in a traffic jam idling, traffic crawling 20 to 50 ft every 30 seconds then stopping over and over again for an hour. I do believe the throttle body heats up so much that it starts cracking the fuel before it gets burned and changes the idle? In my experience the idle starts jumping up to 1800 or 2000 rpm and back down when it gets hot. It has always done this before and after I have changed the ECM, Intake seals, rocker gaskets, K&N Air Filter, Comfort Kit, breather reroute, etc.... whether I have codes or no codes it is the same behavior. I love commuting on the Buell in the winter because it is a nice heater. In the summer I do not commute on my Buell as much and ride more recreationally away from traffic jams. For the summers i commute more on my 2007 Tiger 1050.
    Last edited by Tbone; 10-13-2017 at 11:36 PM.

  7. #7
    @AZmidget91 and @TPEHAK - I also did the intake seal test specified in the manual. I removed the plastic scoop on the left side and the plastic cover on the right and sprayed starter fluid at the intake seals with the bike running and hot. At no point did the revs increase. How do I determine AFV? It is running a bone stock ECM setup with all stock internals, except for a K&N air filter.

    @lunaticfringe - I have removed and reinstalled both the IAC and the rubber boot a couple times today. I know it is installed correctly, and was before as well.

    @Tbone - This is a problem that is far beyond normal intended operation. The bike will die with the clutch pulled in on decel. It's dangerous this way.

  8. #8
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    Actually RPM should go lower after spraying if there is a leakage. Here is intake seal test



    Make sure you spray abundantly all way around.

  9. #9
    Quote Originally Posted by TPEHAK View Post
    Actually RPM should go lower after spraying if there is a leakage. Here is intake seal test
    Using the brake cleaner, like they do in the video, would cause the RPM's to drop. Brake cleaner has Tetrachloroethylene, which is volatile but non-flammable. I used Starter Fluid, which is highly flammable (indeed the manual suggests using propane) and would cause a significant increase in RPM's if it got into the intake system.

    I think that both the IAC actuator and O2 sensors are the problem here. Thinking more about it, the problem decreased in severity after cooling the body of the IAC actuator, but quickly came back when the IAC actuator body heated up again. The IAC actuator is essentially just a solenoid, and if it cannot actuate because it is failing with heat, then it would cause a lot of problems.

    My next set of questions:

    • How can I measure the electrical I/O of the IAC actuator?
    • What are the proper electrical I/O values of the IAC actuator?
    • How can I measure the electrical output of the IATS?
    • What is the proper electrical output of the IATS?
    • How can I measure the electrical output of the O2 sensor?
    • What is the proper electrical output of the O2 sensor?


    I purchased a Buelltooth and Android tablet to check out/reset the CEL codes.

  10. #10
    Senior Member Cooter's Avatar
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    Using the program ECMDroid and the Bluetooth dongle you got from Buelltooth go to "live data" and select those items.

    The specific readings can still be found in the free .pdf manual download from Buellmods.com or Buelltooth.com (where you bought the dongle).

    I hate throwing money at a guess, especially because you are diagnosing this properly (my kudos to you sir) BUT all three sensors are cheap and easy to replace. The O2 sensors like to get lazy and be a PITA before they fail.



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