First thing you need to do is connect a scan tool to the PCM and bring up RPM, desired (idle) RPM, and IAC position data. The PCM will attempt to get the engine RPM to operate at the desired RPM reading by adjusting the IAC valve. Typical IAC position counts at warm idle should be around 30-80 counts. If you are seeing 0 IAC position counts with the engine idling too high, unplug the IAC and then shut off the engine. Remove the IAC valve and see if it is fully extended which should close off the IAC passage in the throttle body. If it is, then you have a vacuum leak somewhere you have not found.
If the IAC valve is not fully extended with the IAC counts sitting at 0, then it is possible your IAC valve is bad or there is a wiring problem.
If you don't see IAC counts dropping to 0 with too high of idle, let me know what you are seeing for IAC counts as well as what TPS voltage is at closed throttle.
-ryan
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More is more. Less is not enough.
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