So my car hasn't been idling at an acceptable engine speed and hunts for idle since replacing some injectors and installing the VG phenolic TB and IACV spacers. (I will make a new thread about this sometime over the weekend.)

Anyway, I removed the IACV spacer and reassembled to see if it made any difference. It didn't.

So I started playing with this thing attached to the IACV stepper motor...



You can adjust it over a full range by removing the clip and spinning it as shown:

 

I am wondering whether adjusting this will affect idle or not, since I haven't completely discovered the root of my idle issue.

There is a stepper motor connected to that thing in the picture and when you turn the ignition to "on" it moves out and then moves back.

My question is if manually adjusting it will do anything, or if the stepper motor "self-centers" it inside the IACV body that it slides into.

One theory I have on it is that adjusting that thing does what adjusting the idle air screw does, just on a greater scale. Yes, no?

 

the idle screw controls a static air passage which bypasses around the iacv stepper valve. messing with that plunger you are playing with, does nothing; it self-centers. so within the iacv there are 2 air passages. one for the screw, one for the valve. If you completely tighten the idle screw, the idle will be fully electronically supported by the steppermotor valve, in accordance with engine RPM and what the ECU tells it to do. The idle screw is nice though, because if your iacv fails then you still have some air going thru the idlescrew passage so you won't stall out and stuff.

alot of people will say that i'm wrong about this, but i've seen an iacv split into all 3 parts, and i looked at it pretty closely, and i saw the screw passage separate from the steppermotor valve passage..

 

+1


The U shaped piece of plastic is there to enable the "threaded metal screw of the stepper motor" to predictably turn inside of the plastic "threaded valve molding" .................... if you remove that you U shaped plastic bit the valve's movement will not be able to be reliably controlled and you will experience erratic idle speed control depending on the friction of the stepper motor screw on the inside of the threaded valve body - IE - you need all those bits to be clean, to be present and to be properly adjusted (with no unaccounted for vacuum leaks elsewhere) in order for the ECU to successfully control idle speed via the IACV.

 

mine is way different though... it's got a hex shaped head and no ubolt at all. fitting the hex plunger into the hex hole is what prevents the plunger from spinning, thus acutating the plunger in and out.

 

Mine is hex shaped too - guess it depends on the exact vehicle/motor model origin as to the source of the IACV - no biggie - the purpose and operation is exactly the same.

 

did you clean it out. i cleaned mine very thoroughly and have had a rock-steady idle since. make sure there is no vac. leak with the phenolic spacer too