What condition of the fuel in an EFI system is primarily managed via O2 sensors?

The fuel mixture in an Electronic Fuel Injection (EFI) system is primarily managed via oxygen (O2) sensors. These sensors play a critical role in the closed-loop control system of the engine. When the O2 sensors detect the amount of oxygen in the exhaust gases, they provide feedback to the engine control unit (ECU) about the efficiency of the combustion process.

If the sensors indicate that the air-fuel mixture is too rich (too much fuel in relation to air), the ECU will adjust the fuel injection to decrease the amount of fuel injected. Conversely, if the mixture is too lean (too much air in relation to fuel), the ECU will increase the fuel injection. This adjustment helps to maintain an optimal air-fuel ratio, which is crucial for achieving efficient combustion, reducing emissions, and maximizing engine performance.

Maintaining the correct fuel mixture is essential not only for power output but also for meeting emission standards, making the function of O2 sensors indispensable in modern engine management systems. Other conditions, such as temperature control, pressure regulation, and ignition timing, are managed by different components and systems within the engine.