If you want a lower idle, you need to set the butterflies so that they actually seal when they are closed. One can't be allowed to hold the others slightly open. Then you change the idle map.thanks. i took it out because i wanted a lower idle rpm. seems to work fine. on another note, when you got your best mpg, was it real hot weather?
The idle control valve opens to a point calculated by the ecu to maintain the set idle.When the engine is cold the ecu looks at 1 map that will richen the fuel /the colder the coolant, and another map that will increase the idle rpm/the colder the coolant.Also the idle control valve opens as the engine revs are increased.
Removing the idle control may cause poor running from cold and will richen the mixture at low throttle.