The idle air control (IAC) valve assembly on a combustible engine monitors and manipulates the amount of controlled air moving around the throttle plate. The IAC valve is managed by the electronic control module (ECM) of the engine, which calculates the position of the IAC valve. Voltage pulses called counts extend and retract an internal conical-tipped shaft called a pintle inside the IAC valve. When the pintle is extended, the cone-shaped tip positions itself closer to the air inlet and restricts the amount of air allowed to pass through the throttle, building up more air around the throttle plate to increase the rpms of the engine. When the pintle is retracted, it moves away from the inlet and allows more air into the throttle away from the throttle plate, decreasing the rpms. The IAC valve operates and adjusts constantly while the engine is running to help prevent the engine from stalling or surging.
A combustible engine needs air as well as fuel to mix and then burn to operate properly. The air fed to the engine is directed into the throttle from a designated point in the engine compartment. Sensors and valves monitor the air quality and pressure before allowing it to pass into the throttle. If a check engine light emits on the dashboard of a vehicle, it is often caused by an emissions failure or problem of some sort.
The throttle valve is a flat, flue-like flange managed by a cable and wheel assembly controlled by the accelerator. The accelerator provides the amount of fuel entering the engine at the throttle location. Because the combustible engine of a car needs air as well as fuel, an air intake system is integrated to mix with the fuel. It begins at the air box where the engine air filter is located. A large opening at or near the bottom of the air box feeds unfiltered air into the box. The air is then filtered by the engine air filter before it enters the air intake tube. A mass air flow sensor monitors the quality of the air as the air passes through it on the way to the throttle body. Before the air reaches the throttle body, the IAC valve is then in charge of distributing the amount of air to the engine to prevent it from getting too much or too little.
