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Thread: Iac

  1. #1
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    Iac

    Anyone know if I can use the screw in type of IAC in place of the original bolt on? Will the ecm know the difference or care. I would like to make an adapter for a custom application and it would be allot easier to make the adaptor with the screw in type. I am using the EFI from 1992 S-10 4 cylinder on a different application (MG Engine) and not using GM throttle body.
    Thanks

  2. #2
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    You can swap IAC's without worry.

  3. #3
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    Thank You

  4. #4
    RIP EagleMark's Avatar
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    I got a lot to learn about those one barrel TBI... I thought only the Big Block TBI unit had a bolt on IAC valve...

    You got a picture of that one barrel TBI?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  5. #5
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    Those 2 barrel TBI's are allot more fun. I had two SS 454 trucks.
    This is the type of IAC and adapter I am currently using. This one is from Patton Machine and the IAC is from S-10 2.5.
    No good picture of the 1 barrel TBI.



    IAC_Small.jpg

  6. #6
    RIP EagleMark's Avatar
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    That looks just like the Big Block TBI IAC.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  7. #7
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    Interesting idea on a way to use a iac.

    Looks like the one on my vortec throttle body, and the one on my YJ.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

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  8. #8
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    The YJ IAC is different. The taper and / or stem length is different. A GM IAC in the Jeep body will overextend and then can't retract.

    Almost all GM vehicles from somewhere around 92 started going to bolt on IAC. Easier and less expensive to machine the TB. Many of them are interchangeable. Aftermarket replacement valves generally have maybe one or two different tapers. L29 454 pfi valv is the only one I've seen that's vastly different.

    Note to OP: You may run into issues with IAC going wrong way after change. ECM commands fewer counts but IAC actually opens. Fix is easy. Swap two, any two, wires on the motor.

  9. #9
    RIP EagleMark's Avatar
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    There's also an issue with BB IAC wiring that has 2 wires swapped. Why? I don't know but it is listed in wiring diagrams if you have issues with IAC control. Maybe this has something to do with what 1project2many is describing.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  10. #10
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    Yes, similar issue. If stepper motor goes wrong way then swap two wires.

  11. #11
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    Can anyone tell me which is pin A on the bolt on iac with the flat 4 pin connector? I'm swapping a big block throttle body into my truck and bought a replacement pigtail and connector for the iac, however the manufacturer didn't use the same wire colors so no luck doing it that way. Ive tried searching, but have come up with nada...
    95 ecsb vortec 357 10.44:1 scr LT4 hot cam single plane TBI 7427 $0D

  12. #12
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    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  13. #13
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    Thanks! Exactly what I needed to know.
    95 ecsb vortec 357 10.44:1 scr LT4 hot cam single plane TBI 7427 $0D

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