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Thread: Low Idle, 100% IAC

  1. #1

    Default Low Idle, 100% IAC

    So after some various teething issues, I finally changed the MSD to a Holley Dual Sync distributor, which has just been fitted and I’m pleased to say it "seems" for now my problems have been resolved. However, a new interesting one has developed. After the first test drive I noticed the idle RPM was a bit too low, when the A/C is turned on it remains just above stall. So I upped the idle (from 850 to 950 RPM). The thing is, the IAC drives to 100%, but the idle won’t increase over about 800ish. Also, unrelated I’d imagine, but the idle timing is about 22/23. It seems to be running very happily at this, but I would have expected closer to 15. Any thoughts?

  2. #2

    Default

    The IAC is at 100% because it is trying to meet the new idle targets. The idle timing is increased as well, because the idle is low, so the Sniper EFI is wanting to add timing (to increase torque output) to bring the idle up. The throttle blades need to be adjusted with the engine at operating temperature so that the IAC reads 2-8% at idle. Page 44 of the Sniper Instructions walks through how to set the idle blades: http://documents.holley.com/techlibrary_199r11031r.pdf
    Right now the IAC is open 100% and giving all the extra air it can to help idle the engine up. You want it mostly closed at idle so that the IAC can react for things like dropping the transmission into gear, alternator load differences & A/C compressor loads.

  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    18,685

    Default

    Opening the throttle blades (idle speed screw "in"), decreases the IAC Position at hot idle.
    Closing the throttle blades (idle speed screw "out"), increases the IAC Position at hot idle.
    If the idle speed screw is unscrewed too far, the engine is inhaling air from an additional source - vacuum leak.
    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

  4. #4

    Default

    Thanks guys, I'll look into it.

  5. #5

    Default

    I have 0-1% IAC at my desired idle. Is that a good spot or should I close the blades some more, so I have more IAC?

  6. #6
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    18,685

    Default

    Around 5% would be better.

    Originally Posted by Danny Cabral
    The Sniper EFI doesn't have the same TPS Autoset function as the Terminator, HP & Dominator ECUs. The Sniper EFI calibrates the TPS sensor
    at every key-on event. If replacing the TPS, the TPS sensor is located at the end of the primary throttle shaft, opposite end of the throttle lever.
    It's slotted, so install it in the same position. Holley 543-111 TPS or Standard Motor Products TH191 TPS.
    http://forums.holley.com/showthread....=2760#post2760 (Replacement Sensors For Holley EFI - Auto Parts Store)

    Sniper EFI Idle Setting/Throttle Blade Setting (Holley Sniper EFI Quick Start Manual):
    Once the engine is up to operating temperature, the idle speed can be set to what was configured in the Wizard.
    To do this, open up the Initial Startup gauge screen that was used in section 17.0. With the vehicle in neutral,
    adjust the idle screw until the IAC Position reads between 2 & 10%. While adjusting the idle speed screw, if the
    TPS Position begins to read higher than 0%, cycling the ignition switch will recalibrate the TPS back to zero.
    NOTE: Do not attempt to set the Target Idle Speed and IAC Position until the engine is above 160°F!
    http://documents.holley.com/199r11193.pdf (Holley Sniper EFI Quick Start Manual - "Idle Setting/Throttle Plate Setting", Page 11)
    https://forums.holley.com/showthread...-Idle-Solution! (Sniper EFI High Idle Thread)
    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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