KTM 990 Idle Speed Control Stepper Motor Operation

Discussion in 'KTM 950/990' started by BillyD, Jul 6, 2010.

  1. BillyD

    BillyD Been here awhile

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    During normal operation (i.e. riding the bike), does the Idle Speed Control (“ISC”) stepper motor ever change position?

    When you first turn on the ignition key, the ISC stepper motor first cycles the main butterflies valves closed (or at least until the linkage hits the stop set screws) and then back to its previous slightly more open position.
    <o:p> </o:p>
    Perhaps this cycling on ignition-on is a means of re-calibrating the throttle position sensor each time the bike is started, but regardless of why it does this cycling, my real question is does the ISC stepper motor ever change positions during subsequent normal operation?
    <o:p> </o:p>
    If so, how so and why? It would be particularly interesting to know if it cycled down to the idle stops during deceleration.


    [​IMG]
    ISC Stepper Motor Linkage



    [​IMG]
    ISC Controlled Cam on Main Throttle Linkage
    #1
  2. cyborg

    cyborg Potius Sero Quam Numquam

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    :lurk ...

    Dammit, now another thing to think about! :lol3
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  3. Oli990

    Oli990 Been here awhile

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    I had to replace my stepper motor at 20000km because idle speed was going everywhere from 1500rpm - 6000rpm while riding. The bike didn't slow down with the throttle closed :eek1
    Dealer told me the stepper motor could not be ordered separately so I had to by the entire FI system + work = 1300 euro :huh
    With the help of this forum I found a second hand FI system took of the stepper motor and replaced it with mine. No adjustment or calibration necessary.
    Problem solved, bike is running fine now :clap
    #3
  4. BillyD

    BillyD Been here awhile

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    The ISC stepper motor controlled cam position shown in the pictures above is what I believe to be the "normal" position while the bike is running.

    The question I have whether this cam moves from this position at anytime other than during initial key-on sequencing?
    #4
  5. Deviant666

    Deviant666 Been here awhile

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    Old thread but this problems seems like a common one (after a certain amounts of kms). My bike now has 92k km (almost 60k miles) and it started doing this. Searching the internet I found that you can actually bypass the idle control motor with 2 x 8.2 ohm resistors (5W). I'm going to give it a try hoping that my idle won't be affected much when altitude or temperature changes dramatically.

    P.S. take a look at this:
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  6. rider911

    rider911 Shortcut Navigator

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    I believe that the stepper is always live, but I dont think it does what you are eluding to. I think the ecu is constantly sampling data from all the inputs and potentially continues to alter the stepper to achieve the preset idle speed. I have had an oscilloscope on the stepper inputs and its is constantly changing albeit very quickly.
    One of my biggest gripes about the FI on these bikes is that the decel engine speed is much too high and wants to push you into the corners. I have had several 990s and I alter the idle via tuneecu back to about 1370 to try and overcome this but the down side is the flywheel is too light and its easy to stall if you do any single track type riding.
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  7. Deviant666

    Deviant666 Been here awhile

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    What would be the consequence of entirely removing the idle control stepper motor? As far as I know the 990's idle at 1400-1500 rpms. Wouldn't just a cable adjustment be enough to make it run without a problem?
    #7
  8. gefr

    gefr Life is a trip

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    Is idle speed adjustable through TuneEcu? My 990Adv 2006 is not.
    Cheers
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  9. Deviant666

    Deviant666 Been here awhile

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    Hello George, no I don't think it is. I was refering to manually adjusting the cable at the throttle linkage (if possible, never done this. I suppose it's doable). I 've tried the reset procedure of the idle motor through TuneEcu with no luck. I never tried to override the idle stepper motor when it worked fine. To be honest, I don't even know if such a thing can be done.
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  10. JoeMongo

    JoeMongo ¿Por dónde? Supporter

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    In the USA, 2007 and later fuel injected 990s allows edits to the idle speed setting via TuneECU. I raised some of the middle of my idle curve just a little due to occasional stalls when the motor was transitioning through the intermediate temperatures while warming up.

    BTW, if my idle stepper ever goes bad, I'll probably remove it and install a bracket with a screw and lock-nut to push on the same lever that the current step motor is driving. Then I would adjust it for the idle I want when cold.

    I would have to figure out a remotely removable shim or adjustable cam in between my screw and the idle bracket shown below (see yellow painted screw directly beneath the stepper motor), so that I could lower the idle once the motor warmed up. Otherwise the idle would drift up to 2000 or 3000 rpm once the motor warmed up.

    Sounds like too much work. Hopefully my step motor will never fail.


    [​IMG]
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  11. Salzig

    Salzig Long timer

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    I know for sure that the idle stepper is always working also with the throttle open.
    Here's a plot of the recording I made with a OBD-bluetooth dongle and the KTM ECU sensors app for android.

    [​IMG]
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  12. Deviant666

    Deviant666 Been here awhile

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    Or you can simply hold the throttle stable for the motor to get warmer.
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  13. rider911

    rider911 Shortcut Navigator

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    Are you sure, Id be surprised.
    The editing happens in the "map" on your computer
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  14. rider911

    rider911 Shortcut Navigator

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    Obviously if you disconnect it a fault code will appear but it will still run (and eliminate the rogue idle issues). Setting up a "choke" cable would work well but it would be more than a few hours work.
    I think an independent stepper motor controller would be the best option with a little adjustment knob on the handlebar. Im sure it would be easy to build for an electronics guy.
    Im not convinced the actual stepper motor is usually to blame, I think its the signal to the stepper that gets corrupted due to poor connections in the harness.
    #14
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  15. gefr

    gefr Life is a trip

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    Could you be more specific please? Where exactly in TuneEcu you find the adjusting tools?
    Cheers
    #15
  16. JoeMongo

    JoeMongo ¿Por dónde? Supporter

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    here:

    upload_2015-9-25_16-32-17.png
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  17. gefr

    gefr Life is a trip

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    Hey thanx. Didn't know that.
    Cheers
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  18. gefr

    gefr Life is a trip

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    So how do we move the curve? Do we select it with the mouse?
    #18
  19. Deviant666

    Deviant666 Been here awhile

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    My bike has developed an occasional high idle issue at 90k km.

    I tried to disable the idle speed control option via TuneEcu and the bike wouldn't start right after I downloaded the map to the Ecu (it would start normally, if you tried immediately after the map download, but when you turned off the ignition once and back on again it wouldn't even turn when you pressed the starter button - nada, not a single reaction).

    I wanted to disable the idle speed control option so as to take out of the equation the stepper motor. Then it would be just the TPS. Has anybody succeeded in disabling that option in TuneEcu?
    #19
  20. rider911

    rider911 Shortcut Navigator

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    I have never tried disabling stepper via TuneEcu but logically thinking, you cant just turn it off and expect the idle position to magically sit in the correct position. By your description, I suspect the stepper has fully retracted once it has been turned off. Now you will have to manually adjust the idle like you would on any other bike without a stepper motor. Personally I wouldnt adjust the butterfly stop on the main throttle shaft (although you could), I would adjust the idle via the adjustment on the end of the stepper as shown in the earlier pics in this thread.

    If you didnt want to adjust anything to test if a chokeless set up will work, you could just start the bike and when the idle is correct at operating temp, just unplug the actual stepper while it is running. My belief is that the stepper will manually hold the idle at that position for as long as it stays unconnected. The down side is it will throw a code on the dash but that is no big deal while you are testing the theory.
    #20
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