Mi16: high idle & no fuel cut-off on overrun
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  1. #1
    Fellow Frogger! KRISKARRERA's Avatar
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    Icon8 Mi16: high idle & no fuel cut-off on overrun

    I thought my throttlebody might be XU9J2-sized so I took it off to measure it and discovered it's Mi16-sized so that's good.

    I cleaned it up nicely with some carb cleaner and then made the mistake of trying to fine-tune the adjustment of the butterflys and Throttle position sensor. She has been a little jerky lately so it wasn't as if I was truly trying to "fix what aint broke".

    The engine idles fine and at the correct rpm. But here's the problem: upon deceleration there isn't always fuel cut-off! And if I take out of gear and let the engine idle it stops at 1500rpm!! Blipping the accelarator returns the revs to normal. Before anyone says, yes the TPS does click when the accelerator is released and yes the TB butterfly valves are not catching in any way.

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    Now, I've tested the resistance for the TPS and all is as it should be. I heard that I should check the TPS voltage with it on car but god knows how.

    I'm really trying to figure out if TPS is on it's way to the graveyard or if the TB needs more adjustment. As it's of a very slightly interrmittant nature I assume is electrical.

    Any pearls of wisdom anyone?
    (PeterT might have already read all this on a certain other forum lol)
    405 MI16
    170bhp
    Le lion va de la force la force!

  2. #2
    1000+ Posts CHRI'S16's Avatar
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    mmm.... i might be stupid, but i thought you cant adjust idle mechanicaly? it has to be an electornic adjustmet?! Changing the position of your throttle at idle just confuses the ECU and reads poor from the TPS.....
    Im not 100% on this but what i do know is idle adjustment must be done via ECU interogation. - Chris

    PeterT? your our ecu go-to man
    ... ptui!

  3. #3
    Fellow Frogger! KRISKARRERA's Avatar
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    Yeah, I know the idle speed is maintained by the idle speed control valve but that only works correctly is the throttlebody discs and TPS are adjusted correctly.
    I don't know how I'm going to fix this because the Haynes manual's method of throttlebody adjustment doesn't take into account the wear that an old TB will have.........
    Then again maybe its the TPS because there's no fuel cut off on the overrun.....
    405 MI16
    170bhp
    Le lion va de la force la force!

  4. #4
    1000+ Posts CHRI'S16's Avatar
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    Kris, i'm out of ideas my friend. - Chris
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  5. #5
    1000+ Posts PeterT's Avatar
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    Back the idle stop screw off another half a turn, then re-adjust the TPS. It's important that the TPS is at the idle position when the engine is. You should be able to here it "click" as you crack the throttle off idle. Alternatively, verify with a multimeter. I can't recall the numbers on the pins, but it goes like this:

    idle - outside and centre pin should have continiuity
    off idle - no continuity between any pins
    wide open throttle - the other outside pin and centre pin should have continuity

    '92 205 Mi16
    '90 Mi16x4

  6. #6
    Fellow Frogger! KRISKARRERA's Avatar
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    I haven't made any further adjustment yet but I had to do a long journey this morning and I noticed this problem disappeared once the engine got up to running temperature. Does that tell u anything Peter?
    405 MI16
    170bhp
    Le lion va de la force la force!

  7. #7
    1000+ Posts PeterT's Avatar
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    Sounds like it justs needs a fine adjustment as described.

    '92 205 Mi16
    '90 Mi16x4

  8. #8
    Tadpole
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    i know its a long shot but isnt overrun caused by the timing being out aswell?

  9. #9
    Fellow Frogger! KRISKARRERA's Avatar
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    No that's a different kind of overrun, there's no overrun at all when I turn engine off.
    405 MI16
    170bhp
    Le lion va de la force la force!

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