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Thread: Slight Throttle Hang

  1. #1

    Default Slight Throttle Hang

    This is nit picky, but id like to try & tune out a slight throttle hang at idle. If I rev the engine, it doesn't snap back to idle. With idle set at 900 RPM, I can rev it to 2000 or 3000 RPM, then when I let off, it drops to 1100 or 1200 RPM and hangs there for a second before slowly dropping back to idle RPM. Is there a way to tune this out or is this just normal?

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    Default

    Check your IAC Ramp Down Parameters, and ensure the ignition timing isn't over-advanced.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

    Default

    Not sure what overly advanced is, but I run about 20° idle timing, 34° cruise, and 32° WOT.
    IAC Ramp Decay Time is 4.0 sec.
    Idle To Start Ramp is 1000 RPM.
    RPM Above Idle To Re-enable Idle Control is 100 RPM.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
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    17,678

    Default

    Try decreasing the IAC Ramp Decay Time and maybe the IAC Hold Position too.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

    Default

    Will do thanks Danny! Is there something to watch for as I decrease time? Like if I go too far will it fall past idle and surge back, etc?

  6. #6
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,678

    Default

    Some engines aren't susceptible to instability when returning to idle. You just have to experiment with it.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #7

    Default

    I have zeroed out the IAC Hold Position altogether. I much prefer it this way. The only down side I've found is with a cold engine, the IAC is very high to achieve my idle speed. When you blip the throttle the IAC of course shuts off to zero & when you let off the throttle it takes a little bit to open back up & recover the RPM. I actually wish the IAC Hold Position was adjustable by engine temperature.

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