Sequential Fuel Injection (SFI)

SFI vehicles can operate in one of 2 injection modes: simultaneous or sequential. In simultaneous injection mode, fuel is injected into all cylinders at same time. In sequential injection mode, injectors are triggered in spark plug firing order. Fuel injection operates in sequential mode under most conditions. Fuel injection will shift from sequential to simultaneous mode under following conditions: when engine speed is less than 300 RPM, when engine temperature is less than 140°F (60°C), and during starting.

If mass airflow sensor malfunctions, ECM will enter fail-safe mode. In fail-safe mode, fuel injection is determined from internal default tables based on throttle position. During fail-safe mode, engine speed is limited to less than 2000 or 3000 RPM, depending on model. When the engine reaches this maximum RPM, it will not go faster, indicating the fail-safe system is in effect and vehicle needs servicing.