My 20V ST has a very low idle on cold start. Its at 400-500 RPM and supposedly its at 1500 RPM. Does this a connection with the water temp thermoswitch/sensor? My thermoswitch is busted coz the aux radiator fan is constantly on, even on coldstart.

 

or do I need to take out the IACV and clean it?

Well if the thermo switch is busted I'd be replacing that for starters, The ECU would be throwing the fan on as a safety feature so the engine doesn't cook as it can't get a proper reference temperature..

 

If that doesn't fix it then definatly look at the IACV..