[ChevyTech]

An IAC count of 20 at the correct idle with it warm and all accessories off shows the throttle stop screw is adjusted well.

With the engine idling faster then it should be, the IAC count will be high.

Once the IAC is unplugged with the truck running, the IAC position needs to be relearned. If everything is working correctly it will do a relearn on its own if driven at fairly steady speeds above 45 MPH.

The ECM does not know the actual position of the IAC. The ECM keeps track of the pulses sent to the IAC and assumes it moved with each pulse sent to it. With the IAC unplugged the ECM can not change the speed so it keeps trying and that is why the count continues to move.

There have been many bad thermostats, even new ones, for several years, that open to soon. These TBI trucks run rich if they run cold and often get heavy deposits on the valve stems so I am glad you ran some SeaFoam through it. You could heat a new thermostat in a pot on the stove and measure what temperature it opens at.

Years ago the NAPA house brand of thermostats were made by STANT. I have no idea if they still are.

I will watch for another log.