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Thread: Dual IAC Valve Question

  1. #1

    Default Dual IAC Valve Question

    Hi. I just got a Holley HP setup and I have dual throttle bodies on a tunnel ram. I was wondering should I run both IAC valves? Or seal one off and just rely on one to adjust the idle? Also, if I were to run both, can I splice into the wires and will it run both IAC motors together? Sorry if this has been talked about before, but I couldn't find what I was looking for.

  2. #2
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    Quote Originally Posted by manaic0586 View Post
    I was wondering should I run both IAC valves? Or seal one off and just rely on one to adjust the idle?
    Usually only one IAC valve is required.

    Also, if I were to run both, can I splice into the wires and will it run both IAC motors together?
    Electrically, the Holley ECU can drive two GM/Chrysler stepper type IAC motors.
    There's no additional channel/output involved. Simply splice each wire to the second IAC motor.
    https://www.yellowbullet.com/forum/s...11&postcount=5 (Similar post by Doug F. - Chief Holley EFI Engineer)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

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    Awesome, thanks for the quick answer!

  4. #4
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    You're welcome.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5
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    Quote Originally Posted by manaic0586 View Post
    Hi. I just got a Holley HP setup and I have dual throttle bodies on a tunnel ram. I was wondering should I run both IAC valves? Or seal one off and just rely on one to adjust the idle? Also, if I were to run both, can I splice into the wires and will it run both IAC motors together? Sorry if this has been talked about before, but I couldn't find what I was looking for.
    It will also depend on the size of your engine. I have a 620ci BBC with a 2000 cfm throttle body, hydroboost & A/C. On initial fire up we could get it to idle fine with the IAC in the throttle body but once you put it in gear, hit the brakes or turned on the A/C, the IAC would run up to 100% and we couldn't keep it idling. We ported both sides of the IAC port in the throttle body as much as possible, which helped a bit, but didn't solve the problem. Added a second remote IAC valve and bingo, problem solved. We used the FAST remote IAC and installed it directly in the manifold plenum. The pintle and sealing port on these valves are only so big, so they are limited in what they can flow.

    It sounds like you have this figured out already, but I wanted to add the comment because when I was researching it people told me there was no way you'll need two IACs. In fact one well known tuner, who I've know for years, told me to ditch the hydroboost and that will solve the problem! I guess power brakes and steering isn't necessary!

  6. #6
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    My previous 508" BBF engine (hydroboost brakes, power steering, alternator, vacuum pump & A/C) had one IAC valve and it worked perfectly.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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