Fuel Delivery and Air Induction: Description and Operation

MULTIPORT FUEL INJECTION (MFI) SYSTEM
The MFI system employs the signals from the heated oxygen sensor to activate and control the injector installed in the manifold for each cylinder, precisely regulating the air/fuel mixture ratio and reducing emissions.
This 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. The two operating modes in the MFI system are as follows:
1. Open Loop-air/fuel ratio is controlled by information programmed into the ECM during the manufacturing process.
2. Closed Loop-air/fuel ratio is varied by the ECM based on information supplied by the heated oxygen sensor.