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Thread: General IAC Info & Ford PWM IAC Wiring

  1. #41


    Finally getting down to the nitty gritty things and making the settings in the ECU. Given that the IAC motor I'm using is from a Ford 5.0L. I chose it, I read through what has been recommended and made the adjustments as directed. Here are screen shots of what I've done. Do these appear to be set correctly?
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    Last edited by jeff@califon; 07-22-2018 at 01:56 PM.

  2. #42


    Hello, I got a question about the GM IAC and I figure that this might be a good topic to post. Recently I decided to try a Wilson 1500 CFM 4150 throttle body on my 500 cid big block Mopar in the jet boat, to replace the 1000 cfm Mass-Flo (Ford IAC) that it had. I was advised to try a bigger throttle body after the Holley HP datalogged a 3 kPa pressure drop at WOT. To make a long story short, the Wilson and its GM IAC would not recover the idle after the engine decelerates. I have tried the various suggested IAC & idle control/ramp settings to no avail. After futilely messing with it and tying up a boat ramp all afternoon, I swapped back to the Mass Flo throttle body with it's Ford IAC and the engine is happy again, with the IAC quickly catching the engine at 1500 RPM, with a 3 second ramp down to 900 RPM. (Ford IAC settings: 55% Hold, Ramp above idle at 600, 400 for re-enabling idle control, with 3 second decay time.) What I suspect is with the engine driving a rather large jet drive, which continuously applies a load to the engine at any RPM, so the engine will decelerate from WOT at 4700 RPM to a 900 RPM idle in less than a second. I have read that the GM will not function as quickly as the Ford IAC, taking up to 2 seconds to fully operate. I tried to set the GM IAC Hold Position as high as 90% with the idling IAC Position reading 0-2%, but it still died on deceleration.

    My questions are, is this a common problem with using a GM IAC in such an application? Is there a GM-style IAC available that operates as fast as the Ford IAC? I suspect that the GM-style IAC and bypass port size is inadequate for idle recovery on a 500 cid engine turning a large jet drive. I'm in contact with Wilson to see if their 1500 CFM throttle body can be adapted for use with a Ford IAC.

    The engine is 500 cid, Indy 440EZ MW ported heads, Indy MW single-plane EFI intake with 60 lb/hr injectors with cam sync. Cam: 237°/241° @ .050 110° LSA. Idles at 57 kPa with 10 lbs of fuel, with AFR of 13.0 for smoothest idle quality at 23° of timing.

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