IAC Valve is a control not a sensor, just FYI
Computer uses Crank sensor for RPM
It then Pulses 12volts to IAC Valve to set air "leak" level passed the throttle plate to set idle RPMs
On a WARMED UP engine, if you unplug the IAC Valve's 2 wires the valve should close all the way and RPMs should drop to about 500 or engine may even stall, either is good and correct.
If idle stays high then you have an air leak doing what only the IAC Valve should do, leaking air into the intake.
Yes, with IAC Valve unplugged manually pull throttle plate closed to see if throttle cable or Cruise control cable might be holding it open.
If not then with IAC Valve still unplugged, pull off ONE vacuum hose at a time and plug that intake opening with your finger, if RPMs drop then you found the leaking hose or device, replace hose and repeat with next hose.
If it is not a hose then it could be a gasket.
Use a spray bottle with soapy water and spray it around gasket areas, you will here idle stumble if water is sucked in.
Some use carb cleaner or other flammable spray for this test, but on a warmed up engine this can be dangerous so just a heads up.
On the throttle linkage there will be a Screw that "looks like" an idle screw, it isn't but can hold throttle plate open too much, you can back this screw off to make sure it isn't holding throttle plate open too much, but return it to where it was if it has no effect.
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