That's a good idea and makes perfect sense! Is there a testing procedure for the IAC?
With the engine at operating temp,when you disconnect the iac harness,the engine should stall or the idle should drop slightly, depending on how far inward the throttle body idle adjustment screw is set.If the iac is just dirty,& not defective,idle will normally bounce around surging up and down. However a defective iac can also cause this,if cleaning it doesn't help.
Mechanical idle is the rpm value you set with the tb screw,with the iac harness disconnected.Computer controlled idle is the idle rpm value the ecu sets,with the iac harness reconnected.Mechanical idle should be set between 550-650rpm then the ecu will control idle above that value.672rpm is the target value the ecu looks for.If mechanical idle is set too high,the ecu might not be able to lower idle to the ecu target.
There are several tests for the iac/wiring. With the key on,the red iac wire should read 10.5-12v.Use the engine block as the ground for the multimeter.With the engine running, the white/lt blue iac wire should toggle between 12-.5v,with the meter leads between the red and white/lt blue wire terminals.If there is a short to ground in the white/lt blue wire or the iac body to internal wiring,the meter will usually not read above 1v during the w/lt blue wire test.With the harness disconnected,meter set to ohms, touch each iac terminal with a multimeter lead.The meter should read between 7-13 ohms one way then when the meter leads are reversed on the terminals,the meter should read OL or open loop,since the iac has a diode in it.This is for 89-93 & all remanufactured iac's.86-88 models had a diode inline with the iac harness instead, while 89-93 models (& all remanufactured iac's now sold) had a diode in the iac itself.If its a 86-88 iac you're testing,both test directions listed above with the meter, should read 7-13ohms.Now touch one meter lead to the iac body and touch the other lead to one iac terminal then move it to the other iac terminal.The meter should read OL or a very high ohms reading for both terminal tests.