Idle Air Control Valve - Engine Braking

IDLE AIR CONTROL VALVE - ENGINE BRAKING


During engine braking and at Closed Throttle Position (CTP), the Engine Control Module (ECM) controls the Idle Air Control (IAC) Valve so that air is supplied to the engine to:

^ maintain the negative pressure in the inlet manifold within bounds
^ improve combustion and reduce emissions
^ control engine braking and how fast engine speed can drop.