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Thread: LS1 IAC overshoot with TH400.

  1. #1

    Default LS1 IAC overshoot with TH400.

    OK, so I've read the idle tuning threads over & over again on here, and I got a nice idle. But my issue now is when I'm in gear and put it into neutral it goes from about 750-800 RPM to almost 1500, runs lean for a few seconds then idle normal again at about 800-850. What setting would help this? Like I said I've read idle tuning threads over & over, just don't understand the terminology. Also, why would my IAC Ramp Down so slow? I have the Ramp Down to just a couple seconds, but I watch the IAC Position on the laptop in live mode and it's starts at like 13% and takes almost 10 seconds to drop to 0-3%. While it does that, it runs lean at idle till IAC closes. Am I doing something really wrong? Truck has Holley HP EFI and a TH400 transmission.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    17,979

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    Quote Originally Posted by Yotaracer View Post
    Like I said I've read idle tuning threads over & over, just don't understand the terminology.
    EFI Software Help Information/Instructions:
    ‒ On the top Toolbar, click "Help" & "Contents". This opens all Help topics.
    ‒ When navigating the software, click "Help ?", drag it to any parameter and click again.
    ..This automatically opens the definitions for that specific parameter.
    ‒ Tuning information can be read by clicking the F1 key, when you're viewing any screen.
    http://documents.holley.com/techlibrary_199r10544.pdf (Holley EFI Help/Instructions Overview)
    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

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    So I need to raise my "D Term" number up?

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,979

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    The "D Term" is only for the Idle Spark control, not the IAC control.
    The Idle Spark control varies the ignition timing to stabilize/control the idle RPM.
    The Idle Spark control is usually enabled at: P Term 30 or 40 & D Term 50 or 60.
    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

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