Can someone explain the purpose of the iac? I'm getting a high idle when i decelerate, about 1800 to 2000 rpm. If i tap the throttle it settles down to 1000 rpm. I've checked for vacuum leaks and i'm sure i have none. The car always settles down when i tap the throttle so i'm thinking it's tps or iac related. As far as i see the iac is whats feeding the extra air. Can i unplug the harness connection to the iac? Other than startup, why else would i need the iac?

 

the iac is CONSTANTLY adjusting airflow into the engine when the throttle plates are closed to keep your car running,your s probably malfunctioning, but it is needed

 

Like he says... Yes it is needed.. Without the IAC.. you will have a constant high idle.. with it completely closed and not fuctioning correctly.. your engine will not run at all.. unless you keep your foot on the throttle..

 

Fuel injection in general doesn't need an iac, but to not have it on one tuned for it would take some adjustment and tuning. I don't run one, but mine's totally aftermarket and made to work how it is.

 

no argument there!!

 

i spoke to ken at first fuel injection and he informed me that the iac needs to be used and that the idle adjustment screw should'nt be used at all. It needs to be backed out and just touch the blade. The iac handles the rest, but he told me to make sure i set the iac correctly from the fully closed position. He is going to email me the procedure to do this.

 

The procedure is in technical articles threads. It's a good step by step process and works everytime.

 

Hey when you get that email can you forward that to me please?

thanks...

 

Wiggle the throttle shaft while looking into the throttle body at your throttle plates. If the throttle plates move side-to-side/up-and-down your leak is probably where the throttle shaft rotates on the throttle-body housing.

I noticed on mine that after lubricating the integrated return spring assembly on the throttle-body that a little gunk had seeped in through the throttle-shaft - ie: intermitten vacuum leak! I have been told before that this may be a common "failure".

IAC is good - it allows for a more consistent idle speed regardless of engine/ambient temperature.

When you decelerate/when you are not at idle - AFAIK the IAC should be fully closed (?). (Or perhaps it just goes to a pre-set point) I may be wrong though.