Low speed miss

Discussion in 'Engine, Fuel and Exhaust' started by jakester, Feb 3, 2011.

  1. jakester

    jakester Member

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    My 2006 heritage has a low speed miss or light bucking at around 10 to 15mph in first gear. It will do it in second also if I'm going slow enough. I'm not talking about slow speed chug (going to slow for the gear). It Idles great, pulls good once out of the low end speed and runs great in the mid and high ranges. I put a new set of Harley plugs in and had the stealer in stall the new style fuel injectors. (06 had a problem with injectors) I've also run some fuel injector cleaner and so for nothing seems to solve the problem. So any feedback would be appreciated. Also I should mention that nothing came up when I pulled the codes and the dealer did not find any either.
     
  2. Hoople

    Hoople Account Removed

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    The bike did not have this engine miss how long ago. It just started to miss without making and changes or modifications.
     
  3. jakester

    jakester Member

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    I've had the bike a year and a half and its always done it. It had stock exhaust when i got it and I've since changed to a set of pipes that look like long shots but I'm not sure what brand (used). I'm running baffles wrapped with fiberglass and they seem to have plenty of back pressure. It pulls good. It still has the stock air filter. Thanks for the reply.
     
  4. Hoople

    Hoople Account Removed

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    What are you using for a fueler or mixture enrichment over factory stock settings. Also, is your bike pre-O2 sensors?
     
  5. jakester

    jakester Member

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    No fueler or enrichment over factory. I believe tech at dealer remaped after installing injectors. No o2 sensors for 06 heritage.
     
  6. Hoople

    Hoople Account Removed

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    Since it idles great and also has strong midrange and top end without any signs of a miss, I would rule out ignition and focus on it being more of a low speed surging than a miss. A lean surge can easily feel like a "miss" but it really is not.

    I can give you a step by step blueprint on what to do but since you have no fueler, your probably just a bit lean and have a lean surge during high MAP pressures. I myself would install a fueler and see if the problem goes away. You can't go wrong adding a little bit more fuel even if it does not fix the original problem.

    Things like an intake air leak or low fuel pressure could give you a lean surge also but since this problem has been on the bike since day 1 you really don't have a baseline. My bike came off the showroom floor with a Terrible lean surge in 1st gear.

    Even the 2006's with pre-O2 sensors were somewhat lean from the factory and would benefit from a TFI fueler.
     
  7. jakester

    jakester Member

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    Thanks for the reply Hoople. The dealer also checked my fuel pressure and replaced the intake gaskets so I think I'm OK there. I think your probably right that a tuner could help. Also just a thought could a bad spark plug wire cause this problem ( bad Ion sensing) or is that a stretch.
     
  8. Jack Klarich

    Jack Klarich Expert Member

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    Check it with an ohm meter and bend it to see if the readings change
     
  9. jakester

    jakester Member

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    Thanks Jack, I guess it dosn't matter what the reading is just that it changes or not.
     
  10. Hoople

    Hoople Account Removed

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    No harm in testing with a meter but in general, if you had an ignition problem, it most likely would show up under hard acceleration. When combustion pressures increase, the demand on the ignition system increases. Since you said "it pulls good once out of low end speed" I put aside it being a spark breakdown issue.

    Nailing the throttle at 2800 RPM in a Tall gear puts about the hardest demand on an ignition that there is. If you could pass that (smooth strong pull without breakup) you probably have sufficient spark energy for the low end.

    It's good that you know for a fact your fuel pressure is good. Good intake seals is another item you can check off the list. New style injectors along with matching map,, Great.
    Your down to the last few.