Does anyone know how to test the IAC to make sure it is funtioning properly? If this device is truely a valve of sorts, it should open and close to allow / disallow airflow. I tried applying 12V to it to see if the little plunger thing inside would move to open or close the airflow path. I heard a little "clunk" sound (typical of solenoids) like I expected to hear, but no movement. I have already read the articles on how to clean it, but cleaning won't do any good if the darn think is broke. Right? Thanks.

Mark Wortham
'98 Contour GL Sport
2.5L Duratec V6, ATX

Here are a few tests from the Ford TSP CD:

Check IAC Solenoid Resistance
* Key off.
* IAC solenoid vehicle harness connector disconnected.
* Measure solenoid resistance.
NOTE: Due to diode in solenoid, place DVOM (+) lead on VPWR pin and (-) lead on IAC pin.
* Resistance should be between 6.0 and 13.0 ohms.

Check IAC Solenoid for Proper Function
* Key on, engine running.
* Bring engine to normal operating temperature.
* Transmission in Park or Neutral.
* Disconnect IAC solenoid vehicle harness connector.
* RPM should drop or engine should stall.

Be carful which direction the test wires are connected to the IAC. If you apply power with the wires reversed, it will damage the IAC. (The diode mentioned above will fry.) The testing procedure in the haynes manual says if you here the little click noise, the IAC is working. If you have a VOM, the resistance should by high in one direction and low (above values) in the other direction.

Thanks for your replies. I am still concerned that this thing may be bad. I am currently in the middle of a rebuild of the UIM and LIM. I am in the process of putting everything back together. If I put this thing back on and find I need to replace it afterwards, is it difficult to remove the IAC with the UIM bolted on? Thanks again.

Originally posted by Mark Wortham:

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...is it difficult to remove the IAC with the UIM bolted on?

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No, IAC can be removed without removing UIM.