Air/Fuel Mixture: Adjustments

The Multiport Fuel Injection (MFI) system is a system which employs the signals from the heated 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 (1) hydrocarbons (HC), (2) carbon monoxide (CO), and (3) oxides of nitrogen (NOx) 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 (ECM) .
2. Closed Loop air/fuel ratio is varied by the based on information supplied by the ECM oxygen sensor.