By-Pass Air (BPA) Valve
BPA valve, mounted on intake manifold, consists of a thermowax material that expands or contracts depending on engine coolant temperature that passes through the valve. When engine is cold, the BPA valve supplies by-pass air into the intake manifold to increase idle speed. The BPA valve closes as coolant temperature increases.
Idle Air Control (IAC) Solenoid
IAC solenoid is an electromechanical device controlled by the PCM. The IAC solenoid is mounted on the throttle body and allows air to by-pass the throttle plate. The amount of air allowed to by-pass the throttle plate is determined by PCM and controlled by a duty signal.
Idle Air Control/By-Pass Air (IAC/BPA) Valve
IAC/BPA valve controls idle speed by regulating throttle plate by-pass air. ISC/BPA valve consists of air by-pass and idle air control solenoid valves. Air by-pass valve functions during cold engine conditions, at temperatures less than 140 F (60 C). Idle air control solenoid valve functions in all temperatures.
The air by-pass valve is controlled by the engine coolant temperature. The idle air control solenoid valve is controlled by the PCM.
Thursday, January 15th, 2009 AT 8:18 AM