Idle Speed/Throttle Actuator - Electronic: Description and Operation

On all models except 1.8L/4-109, the idle speed control bypass air valve (ISC/BPA) controls idle speed by regulating the throttle plate bypass air. The ISC/BPA valve consists of the bypass air valve which functions only during cold engine condition below 140°F and the idle speed control solenoid which works throughout the entire engine speed and temperature range. The bypass air valve functions by sensing engine coolant temperature supplied to the valve while the ISC solenoid is controlled by an ECA output duty signal determined by various input sensors.