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Thread: Last chance for the Uly

  1. #1
    Junior Member
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    Jul 2018
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    Last chance for the Uly

    Last try for the Uly. Ever since I purchased this 09 12XP I've been fighting low AFV and a stutter/miss/surge at low rpm, 1500-3000. What's been done: previous owner changed to k&n and hawk exhaust. Not sure if it was tuned for that, so I purchased buelltooth and have had Dave send me a few maps specific to my issue & set up. Nothing has helped long term, but there have been glimmers of greatness. I know I have an issue that needs to be fixed before a good tune will work. Reset afv to 100 and it will quickly work it's way to 81... or even as low as 77. At this afv it still has the stutter/miss and has no "guts", torque I guess. Locking afv range at 90 does not help the stutter/miss. What I've done so far that has not helped at all: intake gaskets (should have know that was not the issue), plugs, wires, coil, cleaned all grounds, ran new ground from negative to under coil (I know, but worth a shot). I have new tps and new injectors, but I want to know how to diagnose before changing. I'm tired of throwing parts at a problem. I'm looking for a true "if this, then that" test. I have run live data and tests through buelltooth, but what does that tell me? I don't want to go down the road of R&R the throttle body again unless I'm fairly confident based on some sort of test. This is the last attempt for this bike. The stutter/miss is so bad sometimes that it literally makes me pitch forward. I've spent quite a bit on this bike so far, in addition to the listed, and I'm done. Looking for real test suggestions. And yes, I reset TPS after every change. Thanks for the help, it will be fixed or for sale soon.

  2. #2
    Senior Member Cooter's Avatar
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    If this particular job is out of your capability, and considering your frustration level... It might be much more successful and much less costly to take the poor girl to a good V-twin shop for diagnosis.

    Sometimes it's ok to wave the white flag

  3. #3
    Senior Member lunaticfringe's Avatar
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    Feb 2011
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    AmishLand, PA.
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    no need to buy more new parts. have you????????????????????

    using the manual check TPS sensor for ohms read-out. faulty TPS will often times mimic what you just described.

    have you tried a known good ecm? yours sounds suspicious

    have you checked the small wiring harness feeding the rear cylinder injector for chafing/rub-thru? it happens.



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