is it possible to tell if the IACV is bad by appearance?

[emperor_lunchbox]

I have a serious idle problem, I haven't been able to draw patterns when the symptoms happen but every once in a while (seems to be when I idle after driving on the highway for a while) the RPM's drop from around 700 to 400 or so then shoot up to 900 and rapidly drop and rise again. I usually put the car in neutral (auto trans) to remedy, I step on the gas a bit. Anyway, I have a spare motor and the IACV valve looks to be in rough shape, but if it appears to be in better condition then the one on the running motor I will swap it in.Anyway, what can I do to test the current IACV and can I visually inspect the spare?thanks.

[navysnail]

as far as visual goes, it is a small valve with electronics so visually testing may be inconclusive. Tomorow I will look up the specs in the factory service manual so you can check the one you have now and the one on the car.

[emperor_lunchbox]

cool, Thanks.

[navysnail]

valve should have 10 ohms of resistance. with the ignition switch on, measure the voltage of the harness connector. terminal A should be battery voltage and B shoudl have between 7-10V.

[jserrano]

Also check the TPS.

[420sxse]

Could it be the oxygen sensor, or cracked vacuum hoses?