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Thread: Idle Settings & IAC

  1. #21

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    Talked with Holley Tech today. Had me try to shield my ECU wiring, so I placed aluminum foil loosely around the IAC and around all EFI wiring anywhere near the distributor. I grounded those with jumpers to a good ground. (I have a background in electronics engineering. A shield that's not "drained to ground" is basically an antenna.) Still the same behavior, IAC will not hit zero. I had separated all the wiring already, not that any were close, not even to tach or HEI supply wires, let alone the secondary side.
    Last edited by Wrenchhead67; 09-10-2019 at 10:14 PM.

  2. #22
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,490

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    I'm trying to work out why you want the IAC to read 0%. Every EFI car uses the IAC to add additional air over base idle speed. The only time the IAC would ever be 0% is if the engine is idling faster than target idle speed, and the ECU is trying to lower the speed by closing the IAC to 0%. Gary
    Regards, Gary

  3. #23

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    Thanks, Gary. It's not that I'm trying to set it at 0%, rather I'm seeing if the IAC is operational. I set the throttle blades per the Holley instructions and have also tried blocking the IAC and setting RPM to 50 less than target. I'm troubleshooting, if the IAC says (handheld) it is at 0%, yet the IAC inlet is sucking air like a 3-8” opening, I think commanded IAC and real life are a little off.

  4. #24
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,490

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    So what's your current hot idle speed, and target idle speed? I.E.: How much higher is the true idle compared to target? Gary
    Regards, Gary

  5. #25

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    Thanks Gary. If you go back to posts #1 & #2 in this thread, IAC would not help hit my cold idle of 1100, then 1050 at around 120°F. Would stumble when cold, IAC would go to 100%, as mentioned in #1, I take this as the IAC is opening, trying to smooth idle and reach target RPM at that temp. Even when up to 180°F, I would see IAC going to 100%, and idle was less than 800 RPM I had set as the target. When IAC was set anywhere above 20%, it's sucking like an open PCV hose. I’ve been told, at idle, it shouldn’t be sucking any air, or at least very little. It's sucking enough to raise the RPM 200+. Todd

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