California Models

The multiport fuel injection system is a system which employs the signals from the oxygen sensor to activate and control the injector installed in the manifold for each cylinder, thus precisely regulating the air/fuel mixture ratio and reducing emissions.
This in turn allows the engine to produce exhaust gases of the proper composition to permit the use of a three way catalyst. The three way catalyst is designed to convert the three pollutants: hydrocarbons, carbon monoxide, and oxides of nitrogen into harmless substances. There are two operating modes in the MFI system.

1. Open-Loop: air/fuel ratio is controlled by information programmed into the engine control module.
2. Closed-Loop: air/fuel ratio is varied by the engine control module based on information supplied by the oxygen sensor.