Idle Control System

See IDLE AIR CONTROL (IAC) SOLENOID under SOLENOIDS under RELAYS & SOLENOIDS. Curb idle and fast idle speed are controlled by Powertrain Control Module (PCM) and are not adjustable. Some throttle bodies have a sludge-tolerant design with a special coated throttle bore. A Yellow/Black warning decal on these units warns against backing off throttle plate adjustment screw to avoid throttle plate sticking in bore. Faults in idle control system components or circuit should set a service code. Proceed to QUICK TEST in appropriate TESTS W/CODES - EEC-IV article in the ENGINE PERFORMANCE section.