Initial Setup of TBI, TPI and MPFI systems. Min Air Adjust, TPS set and Fuel Pressure

[EagleMark]

I have often wondered if there was a way to "bench" test a IAC. Any more info on this tool? Is it electrical or what?

I've done that on my test bench, the plunger extends all the way and pops out!

[JeepsAndGuns]

So basicly 12 volts has to be "pulsed" to either extend or retract it? Like grounding one wire, then quickly touching and releaseing the other to a hot wire?
I have a couple spare ones from a old dodge tb, I may play with them, if I burn it up there is no loss...lol

[EagleMark]

My test bench is not running, I'm in the middle of building a harness or I would check for you. Pretty sure 12 volts will burn it up. It's a 5 volt signal... IIRC

[JeepsAndGuns]

Ahh, good to know.

[88ragtop]

This article explains pretty well how the various types work: http://www.megamanual.com/ms2/IAC.htm. Just read around the megasquirt configuration stuff that you dont care about :)

- Frank

[1project2many]

A stepper motor like the IAC need to have power and ground applied to different terminals to make the armature turn a complete revolution. Look at the gm wiring diagram for your system and you'll see two connections for coil A and coil B. Each of these needs to be connected to 12V in turn on order to make the IAC move. When the ECM shows IAC counts, that's how many times the ecm has applied power to one or the other coils to make the IAC move. I have an old tool made by Thexton but I couldn't find it in their current tool lineup. Here's a thread that gives a homegrown way to check the IAC: http://www.chevytalk.org/fusionbb/sh...96c4b37436442/ There's also a mention of an OTC3320 IAC tester but I really think those old tools are only going to show up in Ebay auctions or swap meets now.

[EagleMark]

You sure it's 12 volt? I wasn't... then read the IAC procedure .pdf and it says do not apply 12 volt... ?

[Mastiff]

I tried this procedure and when the A/B pins were shorted the IAC made noise and never stopped. Just kept sort of buzzing. Well, I didn't wait forever, but 30 seconds or so. Should it take a long time to bottom out, or is something wrong with my IAC?

Also, you specifically said to have almost no pressure on the return line. Why is that important? I've never checked it, but I am using a section of my original 1/4" steel return line, which may be on the thin side.