Have you checked to make sure you throttle position switch is clicking on and off when you put the throttle in and out of idle? It's easy for these switches to get out of adjustment if you've have the TB off for a cleaning. Though switching out the TB means that that's probably not the cause, it's worth a quick check.

Sounds like the IAC is in the failsafe-open position. The ECU won't send idle-control signals to the IAC unless it sees the throttle-closed input (from the little switch by the throttle on firewall side). Check the switch adjustment (should 'click' when the throttle is moved off idle), the switch contacts themselves, and that the IAC motor isn't open-circuited.

IAC is staying open for some reason - maybe defective temp sensor? This could explain rich mix and high idle because the ECU thinks the engine is cold.

Quick fix of the idle speed is just to plug one of the IAC 3/4" hoses. I used a piece of rubber (like inner tube) about 2-1/2 inches in dia. Pull off the IAC inlet tube, put the rubber over the nipple and reinstall the IAC tube over the rubber, then use a hose clamp. Ther are other better ways but this is what I had on hand at the time.

Could your throttle cable be binding? Perhaps its not fully returning to idle position. My gas pedal used to stop at halfway as the previous owner never used the pedal past this spot. Pushing past this stop would sometimes cause the cable to stick momentarily. Scary.

Erich
Ottawa Canada