slight misfire

Discussion in 'Engine, Fuel and Exhaust' started by nascar7613, Mar 21, 2012.

  1. nascar7613

    nascar7613 Active Member

    2006 Road King fuel injected, no modifications. When running down the road at a steady speed and fairly low RPM, say around 2500, every once in a while the bike will have a very sudden and slight misfire. It will rerpeat this randomly. I wish I could make the noise for you. It doesn't seem to do it until the bike is warmed up. Changed the plugs and wires, no difference.
  2. TripleJ

    TripleJ Senior Member

    Might start by checking for DTC's.

    When this happens are you losing losing power to the lights, speedo or anything else that may be noticeable or is it just making the misfire with no other noticeable conditions? Also what modifications, if any, have been done to the bike and did this possibly start after any recent mod was performed?

    BUBBIE Well-Known Member

    I would ask? How do you know the speed RPM of the motor?

    Could it be the miss is from a Little lugging?

    What gear and what speed on the odometer does the miss happen... this will tell me more than a guess at the RPM.

    I don't doubt your ability to judge RPM but Speed and Gear is easier to supply accurately for us... IF you go slow enough in a gear and Not doing the RPM you think, it may be the problem.:D

  4. nascar7613

    nascar7613 Active Member

    I would be going 50 MPH in fourth gear. I did the wow test and there are no codes.
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    Warm the bike up (riding it) then carefully work your hand in to the injectors and grab the injector wires about an inch from the plug. With the engine running at a fast idle (2k), wiggle the wires on each injector (separately) and see if you can replicate the missing symptoms. If so, you probably have a bad (cracked or broken) wire and will need to fix that.

    Harley Davidson Community

    Last edited: Mar 21, 2012
  6. Hoople

    Hoople Account Removed

    No modifications? Not even fuel enrichment of any kind? Does your bike have O2 sensors? How many miles on the bike. The bike was running fine and then this started suddenly? When you feel the miss,, if you applied more throttle, does the bike pull fine without a miss? This engine miss is ONLY at steady state throttle?,, starts fine,,idles fine,,acceleration to get on interstate is ok?
  7. nascar7613

    nascar7613 Active Member

    The bike does not have 02 sensors or fuel enrichment. It has 43000 miles. The problem came on gradually, every once in a while I would feel something that felt like a miss, now it is every time I ride it after it is warmed up I can feel and hear it. It starts fine, idles fine and when I accelerate there is no miss, only at steady throttle .
  8. Hoople

    Hoople Account Removed

    Could be 1 of several things but where I would start....
    Since it does not happen during mixture enrichment times (warm up w/ extended injector duration or "choke" times), it almost points to a lean fuel issue or a lean miss. As soon as the warm-up enrichment period ends, the bike experiences the miss.

    Something like lower than normal fuel pump pressure, a small air intake leak, 1 injector having a poor fuel spray pattern, fuel filter having poor flow, a pin hole leak in the Hi pressure fuel pump line inside tank, etc. Something that creates a leaner than normal mixture. Anyone of these issues usually gets worse with time, just like your problem has.

    For now I would rule out electrical or ignition since it does not happen under hard acceleration. That's the time when the ignition system is under highest demand.
  9. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    Hoople has got you started in the right direction. Definitely sounds like a lean issue. If it were a Johnson outboard, I would say it is running perfect.
  10. Jack Klarich

    Jack Klarich Expert Member

    Along with Hooples great advice have a look here also Harley Davidson Community