Diagnosing Idle Air Controller on EFI

[hc37180]

Been trying to diagnose some idling issues. Vehicle started idling about 3-400 higher than normal. Will at time go back to normal but when driving around it will constantly stay up around 1100rpm. I have read up that issues can be dirty Idle Air Control (IAC) and/or throttle body. I also read in a service manual that you can put a tester across the leads on the IAC and it should have like 7-13 ohms resistance. I tested it (reversing the connections to make sure I had all bases covered) and the ohmmeter pegged off the charts in the negative direction. Am I to assume that means the IAC is shot? Anyone ever replace this unit on their EFI?
Thx

 

[DirtDonk]

Not sure about the testing procedures, so someone else can chime in on that, but what about the computer? What model is it, and what trans are you using?
And do you have a VSS in the system?

Reason I ask is that even though it sounds like your problem is kind of inconsistent, it's almost like the same issues some have where the ECM is expecting a signal from a VSS that's not there.
Especially certain year automatic ECM's.

Another question. Has it been doing this all along, or did it just start out of the blue?
Is this new-to-you, or did you do the conversion yourself?
Ok, so that's like 3.5 or 4 questions, but enquiring minds need to know...

Paul

 

[EFI Guy]

Paul has a good list of questions there. Is the motor stock or modified?
First things I would do is clean the T/B, IAC, and MAF. Then verify your TPS voltage. If the TPS is out of range it will default to a higher idle speed.

 

[Viperwolf1]

It sounds like you used the ohmmeter on a powered circuit. You can't do that. Make sure the power is off or in this case unplug the IAC first.

 

[Steve83]

Study this caption, and follow the links in it: