929 V6-3.0L DOHC (1993)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Speed Control System
PURPOSE
To provide correct idle speed over the full range of operating conditions (starting, idle, running), system regulates the amount of intake air allowed
to bypass the throttle valve.
LOCATION
Bypass Air Control (BAC) valve is next to the throttle body.
OPERATION
The BAC valve consists of an air valve that functions only when the engine is cold and an idle air control solenoid valve that operates throughout
the engine speed range.
The air valve is the thermowax type. It is open when cold to allow bypass air into the dynamic chamber, increasing idle speed to shorten warm-up
time and ensure good driveability. As the thermowax element is heated by engine coolant, the wax expands, gradually closing the air valve.
After engine warm-up, the PCME controls the idle air control solenoid to maintain good idle quality. To make proper idle speed adjustments, the
PCME monitors inputs from these devices:
