IAC – Idle air control

Chapter 8
What we need to do..
•	Keep A/F ratio at best at all times:

•	Input - Examine a signal
•	Process - “look at” the signal
•	Storage - store the signal for future reference
•	Output - Decide to do some action because of a signal
What we need to do..
•	Control Idle
•	Idle High – Cold engine
•	Power steering
•	Alternator Loads
Types
•	Stepper Motor – GM/Jeep
–	Steps in and out
•	Duty Cycle Solenoid – Ford/BMW/VW (common)
–	Pulsed on and off
•	Rotary Valve – Honda, GM, others
–	Motor – faster = More air

Basic Problems
•	Idle too high – wrong idle set
•	Idle too low – “”
•	Idle too high – Vacuum leaks
•	Idle too low – Carbon/Sludge buildup
•	Car stalls – IAC jammed up or sludge

Setting Idle
•	Follow the book!
•	Clean the TB or IAC
•	NEVER ADJUST HARD STOP SCREW ON THROTTLE PLATE!
•	Only adjust bleed for IAC!
•	Some idles are only adjustable with a SCAN tool!
•	After adjustment, check RPM with SCAN TOOL!