[bl420]

FITV is the one you should be looking at. it regulates the idle during cold startup... using the coolant temperature. as temperature rises the valve/plunger closes. its purely mechanical..

the IACV / EACV whatever you want to call it is ECU controlled... more or less to maintain idle speed. having the ports clogged up you'll probably just notice a shitty idle.

 

[bl420]

fast idle thermo valve

 

[bl420]

if you take off the brass plate on the FITV you can make sure that the ring (has 2 slots on opposite sides) just make sure thats tightened down.

from time to time it loosens up and something happens to the plunger where air would bypass the valve and create an erratic idle.