Intermittent Idle problem

Discussion in 'Electrical' started by gs34, Oct 28, 2012.

  1. gs34

    gs34 Junior Member

    Over the preceding year, I have had an intermittent problem...and by intermittent, I mean it might show up today and last for an hour, or all day. Then it might not show up again for a month...or it may show up tomorrow.
    When it occurs, it will sometimes clear by turning the ignition off, then restarting the bike. Sometimes it will clear after the bike has been stopped for a while, and when it is started again it will be fine.
    I can always tell when the problem is starting because I will begin to get a lot of popping on deceleration, and when I roll to a stop, the RPM will fall to 500-600 and will not recover to idle. If left untouched, the engine will quit.
    During this entire time, it has never thrown a code, and the engine fault light has never come on.
    I have been all thru the bag of tricks....checked and readjusted the throttle cables....checked freedom of movement of the throttle plate....cleaned the IAC several different times, and checked its operation.
    Don't even know how to go any further in troubleshooting this because ...when you stop the bike to try and troubleshoot...the problem is gone.

    Since the weather has turned colder, a couple of times lately the RPM has stayed high (1400-1500) on startup and remained high until the engine had been run long enough to reach normal operating temperatures...or the ignition shut off...and the bike restarted......But here's the good part.....It FINALLY threw a code... PO122...Throttle position sensor open/low
    I'm hoping that this is the root cause of both of these problems. I've bought a new sensor, and will be changing it out sometime this week.
    Does anyone have any other ideas??....I'm open to any and all suggestions.
    Bike is a 2007 FLHTC with 93,283 miles on the clock
  2. Hoople

    Hoople Account Removed

    The TPS would certainly be a good place to start. With 93K on the clock, I would also go ahead and change the IAC because your going to be right there with the tank off changing the TPS. You can only clean an IAC so many times before their shot. They are really more mechanical than electrical and the leadscrew just sticks, wears out and binds. Last time I checked, they were not crazy expensive either.

    The fact that the problem sometimes clears with a re-start points to an IAC. The IAC is told to park and re-step to an idle count position on an ECM re-boot.

    Hey, Congrats with having 93K on a 2007. You must ride!
  3. gs34

    gs34 Junior Member

    I can change the TPS without pulling the tank off, so I'm going to go for the easy fix first....hahaha....But you are correct, and I will probably look seriously at replacing that IAC. Especially if this TPS doesn't cure the problem.
    With this weather moving in, it's going to be a few days before I'll be able to see what happens.
    Thanks for the reply Hoople. That's sound advice.
  4. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    I see you said you already did this, but check this:

    Harley Davidson Community

    Then I would check for pin-holes in the fuel lines.