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Thread: Trying to sort through all the IAC wiring info and other random questions.

  1. #1

    Default Trying to sort through all the IAC wiring info and other random questions.

    I've purchased an HP EFI system to replace the EEC-IV on my 1992 Mustang. I've been searching & reading on the topic of IAC motors, as well as Ford TFI and having a bit of "information overload syndrome". I've read quite a bit on Ford applications. Based off of what Danny Cabral has said about using the TFI for crank/cam sensor & accuracy issues, and how Holley no longer advocates using the Ford TFI setup, I went with the Holley Dual Sync Distributor, which is plug & play. This eliminates the TFI as well as another wiring adapter.

    Along that line of thinking, I started to research wiring for the IAC motor. You read some posts how the Ford IAC is "better" and you read that it isn't. It also appears that if you want to run the Ford style, you have to use up one of the manually configured inputs, and on the HP system there aren't very many. What I decided on is to use a later style GM "push-in" IAC along with a Accufab adapter that makes it, so I can mount the GM IAC to my Ford style TB. This will allow me to use the prewired IAC connector on the HP wire harness. Where the confusion comes in, is about the need to reverse the A & C pins in the connector harness. The specific IAC I'm going to use is a FAST 307059, which is described as "GM LSx Style" IAC. I've read posts about the needed switching of these pins, but I'm confused as to why that would be required if I'm using a GM IAC which this connector is supposed to be configured for? Am I perhaps mixing up instructions somewhere? I guess a better way of asking my question would be, if you have to switch the wires in a prewired harness with a dedicated connector on it, what sensor is this harness designed to work with as "plug & play?"

    I want to avoid using up manual inputs and have as few "spliced" connections on my install as possible. I figured that using the Holley Dual Sync distributor and a GM LS style IAC go a long way towards meeting this goal, but I also don't want headaches and end up chasing my tail when it comes time to fire up my project, if there's mistakes in the wiring setup. Do I need to re-pin this connector or not? Sorry for the book post guys, I just want to get this right the first time. Thanks in advance for any input.

  2. #2
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    The correct IAC motor depends on which Holley EFI system/main harness you have.
    http://forums.holley.com/showthread....neral-IAC-Info (Scroll down to "IAC Motor Harness Connector PIN-OUTS".)
    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

    Lightbulb

    Thanks for responding so quickly Danny. I have the Holley 550-606N system, I'm not at the shop, but I think it uses the Holley 558-104 main harness? The 558-104 harness IAC diagrams says:
    B1-A
    B9-B
    B8-C
    B2-D
    I think in reading this LINK, I have my answer as to why I DO have to switch A & C. It's not a Ford-GM thing, it's a CHRYSLER-GM thing?

    PASTED:
    "Customers buying the Holley EFI systems do not realize that Holley likes to use Chrysler IAC motors, because they flow more air than a standard GM LS style. If you are configuring a system that uses a "standard" GM IAC you will have to make a minor wiring change in order for the IAC to work."
    So the answer to my question as to what sensor this harness is pinned for originally appears to be for a CHRYSLER IAC, and that means not only Ford guys have to re-pin it, so too do the GM/LS guys? Is that correct logic Danny?

  4. #4
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    Yes, your main harness uses the Holley/Chrysler IAC motor (Holley EFI 543-105, or Standard Motor Products AC416). Simple as that, no rewiring or repinning!
    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
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    The easiest thing to do would be to look at the wiring diagram, get the colors of the wires for that IAC plug, then look at your plug and see how it is wired. Then put a meter on the pins for your IAC and see which one you have. Then change the wiring if it's needed.

  6. #6
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    Actually, the easiest way is to use the IAC motor that's plug & play with your main harness (post #4).
    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
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    I should've started my statement with, "If you are unsure of which IAC or wiring harness you have".

  8. #8

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    Quote Originally Posted by Danny Cabral View Post
    Yes, your main harness uses the Holley/Chrysler IAC motor (Holley EFI 543-105, or Standard Motor Products AC416). Simple as that, no rewiring or repinning!
    So just to make this 100% clear, as far as physical size, the IAC motors you just linked me to are the same as the GM, so either one will work with the Accufab adapter to mount on my Ford style throttle body? Perhaps Holley could offer that same adapter and make this process that much easier for us Ford guys. Thanks for the replies, much appreciated.

  9. #9
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    Yes, the Chrysler & GM IAC motor are physically the same (interchangeable), but they're wired differently.
    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

  10. #10

    Default

    Repinning is also pretty easy. Here's a video: https://www.youtube.com/watch?v=6dfi...ature=youtu.be

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