Purpose

The basic function of the air/fuel metering system is to control air/fuel delivery to the engine. The best air/fuel mixture to minimize exhaust emissions is 14.7 to 1, which allows the catalytic converter to operate most efficiently. Fuel is delivered to the engine by individual fuel injectors mounted in the intake manifold near each intake valve.

The main control sensor is the Healed Oxygen Sensor (HO2S), located in the exhaust manifold. The HO2S tells the Powertrain Control Module (PCM) how much oxygen is in the exhaust gas and the PCM changes the air/fuel ratio to the engine by controlling the fuel injector on time. Because of the constant measuring and adjusting of the air/fuel ratio, the fuel injection system is called a Closed Loop system.