IAC valve bad?

[Jmarty]

Hello! Im a new member but ive been lurking around for a couple years. A synopsis of my intro is im an American with little experience on the RB engine family. Anyway…

 

i changed my spark plugs, went to startup the car as a final verification check, and now its idling very high. I know this topic has been beaten to death but heres what i did to troubleshoot. 
 

saw on another post disconnecting the TPS and seeing if idle is affected will tell you if the ecu idle screw is adjusted correctly. If it doesn’t change then its fine. I did this and idle stayed very high. Reconnected that and went to look for vacuum leaks.

All lines seem fine and covered up any cracks with tape temporarily and still no change. 

then thought “screw it” and unplugged the iac to see what happens, and immediately idled fine… a bit low but fine. I think this rules out the spring being stuck because then it would keep idling high even with no voltage correct? As soon as i reconnected i heard the iac take in air and open and up went the idle with it. 
 

any input? Could it be a short or is the iac garbage? 
 

its a R33 GTS RB20E/auto (yeah i know but it was a steal cant blame me)

For now i adjusted the screw on the valve itself to about 1000RPM (i know its not recommended but its just a bandaid for now hahah) but looking for advice if i should just replace the valve or if maybe shoot some wires? 
 

either way both require a trip to the store.

 

Any help would be awesome. Sorry for the beat to death topic again.
 

 

Edited June 27, 2022 by Jmarty
Grammar

[Jmarty]

Heres a video of what happens when i unplug the IAC. 

 

 

[joshuaho96]

You have to figure out what the ECU wants. If the AAC valve is going to maximum opening because it's commanding it to be that way then replacing the AAC valve or fixing the wiring is not going to fix it. Also, keep in mind that for engine stability reasons I'll often see the AAC valve hang open in cases where you would expect it to close. The ECU is doing this by design. So one possible explanation for what you're seeing is the ECU sees the idle switch is off because the TPS is improperly adjusted and advances timing with what it believes is a sane value for the AAC valve causing the idle to race up like crazy when you plug the AAC connector in. Try a multimeter on the AAC valve pins to rule out the 100% duty cycle theory.

[Jmarty]

Youre a life saver! Borrowed a multimeter from work and sure enough was out of spec. Thanks a million!