Use the FAQ's information on the on-board testing for the Bosch 2.4 system if you have it. It will open and close the IAC in one of the tests and you can hear it going "shii-thpock shiii-thpock" open and shut.
Alternatively, I think you could check the IAC by having the car running and applying voltage to it while it's running. If your car revs, then the IAC works.
The LH2.4 OBD system also includes a test that will tell you if the idle open/wide switch works. I hope you have it. If not, you should have continuity between the center and pin... well, on a turbo, the pin closer to the engine, but on N/A I'm not sure.

Make sure you adjust the idle by adjusting the set screw so that the TB completely closes.

BTW if you really need to bypass it, disconnect the IAC and use the set screw to set a minimum idle. This will give you a varying, uneven idle, but it should idle.

-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond