Idle Speed/Throttle Actuator - Electronic: Description and Operation

Throttle Body Component Location:

PURPOSE
The Idle Speed Control By-Pass Air (ISC-BPA) valve controls idle speed by regulating quantity of throttle plate by-pass air. This permits control of cold engine fast idle, no touch start, hot engine idle speed, and engine idle load corrections.

LOCATION
Side of throttle body.

OPERATION
For cold engine operation (below 140°F, 60°C), by-pass valve operation is controlled with a thermo wax element contracting and expanding from variations in engine coolant temperature. After engine warm-up, the ECA controls the ISC solenoid valve with a duty signal to maintain good idle quality throughout the entire engine speed and temperature range.

CONSTRUCTION
The ISC-BPA valve is two components; the by-pass air valve and the idle speed control solenoid valve.