Port Fuel Injection

Port fuel injected vehicles can operate in one of two injection modes, simultaneous or sequential. In simultaneous injection mode, fuel is injected into all 4 or 6 cylinders at the same time. In sequential injection mode, the 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 the following conditions: engine speed is less than 300 RPM, engine temperature is less than 140°F (60°C) and during starting.

If airflow meter malfunctions, ECU 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.