Here is the story, using Craig's software my IAC target and present counts aren't complementing each other. For instance, the target would be 0 but present is about 70 or 80. The present would climb up to 110 by itself (while the target stays at 0) and then when the target goes to mid 100's the present drops to 90ish. This goes on at all different counts but most of the time the target is 0 and present counts are usually pretty high.

Anyone have some comments on this? Is my IAC dirty/worn out?

 

I don't really know how the CM figures target IAC, but I would think it's ok.

There are a zillion things that determine when and where the IAC should be. I've been trying to figure out source code recently and all I can say is I get lost in the sea of IAC calcs.

The throttle plate position affects the IAC the most at idle. You can command the IAC to be at 5 but if the throttle plates aren't open enuf it won't ever get to 5 counts because you have the idle RPM set to 650 (for example).

 

Yeah, I think that the software shows how many steps for the IAC to move. So a target of 0 would tell the IAC to stay where it is. Also I think my IAC was bad... I had to buy a new one due to a freaky IAC checking accident. The procedure I made up went horribly wrong and caused the IAC to shoot the pintle across the motor. I found the pintle, but not the spring.

So here is the warning. DO NOT (under any circumstances) remove the IAC, ground the ALDL wire, and turn on the key while the IAC moves the pinlte to the closed position. If you do good luck finding the parts.

I think it was a bad part though since the keyway in the IAC housing was pretty well rounded off. It may have let the pintle rotate when it wasn't supposed to!

 

If you're going to get serious about EFI, then I would suggest you get a Stepper Motor Driver Kit.
I believe Rainbow Electronics Kits sells one.
Junk the motor that comes in the kit, and change the cap for the 555, to slow it down. Then wire an IAC connector to it.
They were about $25, and that's cheaper then a new IAC.
Makes cleaning an IAC a piece of cake.

Sleeping at a Holiday Inn Express may make assembly easier.


99% of all the IAC problems are from the min idle being set wrong, or the IAC channel being glooped up.

With the IAC FULLY extended, and unplugged, the EST wire disconnected, I set the idle to the min commanded RPM in the code.

Then shoot for having a 0 IAC count at idle.

You might perfer other settings...

 

I was always under the impression that you didn't have to disconnect the EST while setting the min air settings.

Also, if the IAC turns out to be bad that is $80 you've spent instead of 55 for a new one. Sorta works better to buy a new one and have the piece of mind that comes with a new part.

But what have you come up with to check a one wire O2 sensor?

 

Hahaha...been there, done that!

 

A) Like I said you might perfer other settings.
I hate having an engine stall in traffic, and will play lots of games to min the IACs effect on idle.

B) A NEW IAC?.
I have no idea of what your talking about. I've never bought a new one.

C) No sense in testing em, grab a couple used ones next time your at a junkyard. Last Aug, I bought a NEW O2 sensor, and then replaced it twice cause I got 3 bad NEW ones in a row.

I use a DIY-WB when tuning and the oem is used just as designed, just to swing Rich to Lean.

 

Sure we can all laugh about it now but imagine how you would feel if you lost the spring! The worst part is that I blinked and have no idea where everything shot off to. The stupid thing could have gone anywhere! It was dumb luck finding the pintle lying under the car.

Grumpy, yes you are right. But my motor doesn't stall in traffic, just idled wierd. Also I can't find any TPI motors in the local junk yards (do they use these IACs in other application?). One of them even takes out every chevy v-8 and sends them overseas. So if you can find them then test them, but since they are few and far between here I'm forced to stick to my limited options.