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IAC not working. Very HOT to touch

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Old Aug 26, 2015 | 07:33 PM
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Default IAC not working. Very HOT to touch

I have a mild built LS1 that i reused the FAST throttle body I had on my previous build. Got new motor fired, but soon after had a high idle (1200-1400) that would only sometimes come down to 900 once warm, but never to 750rpm like i was trying to command it. I have BS3 computer...it's calling for 17 or more steps, and seeing 0 steps.

Went to swap in a known working IAC and the current one is scorching hot to the tough. Swap IACs with friend's motor, my IAC works on his, his IAC doesn't work on mine.

The IAC is definitely still getting power - once you key on and key off, the IAC cycles to reset itself (backs in/out).

The hot to touch to me seems like that would have to be the IAC shorting itself out, if the wiring got pinched or shielding skinned off or something. Has anyone ever encountered a hot IAC?

I tried to ohm out the wiring at the pigtail only, and none of the 4 pins would ohm out to any of the other - which seems to me that the wires maybe aren't pinched. I have not yet tested the wires from ECM to Pigtail to make sure they're not broken, I also have not tried to measure each pin during key on / running (what kind of voltages should i see at each?)

Right now I'm running a manual IAC (uninstall, screw the plunger to a certain amount, reinstall) which is a ton of fun.

If anyone has any ideas, please help! thanks!

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Old Aug 26, 2015 | 08:34 PM
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Could it be cross-wired? Have you checked the pin-outs against the diagram?
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Old Aug 26, 2015 | 08:52 PM
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It wasn't rewired since the previous build. It worked fine with the old motor. It also worked fine for the first hour of the new motor running.
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