Remove the IAC & you will find the pintle, the end that does the airflow work, it looks like a flattened cone. Clean it & the port where it goes real good.
Check the resistance on an ohmmeter on the ohmX1 scale

I I I
I I I

is what the pins should look like. Check the upper center to the upper left, then right, do the same with the lowers. I believe the reading is around 28 ohms at each reading.

If all reads well, dissasemble & use 3 in 1 oil to lubricate the inners & reinstall.

Now, if you still have the same issue, it might be the adjustment on the throttle body. It's a screw on the top back on it. You might have a plug sealing it, too.

If that doesn't do it, the FSM states that you need a new throttlebody.

I would try the Seafoam througth a vacuum line also, to clean deposits from the intake manifold that might be clogging miniature airways.

If it all fails, wires, plugs, air filter, air leaks in intake tract, dirty injectors...

Ed