Closed Loop Mode

The engine is in this mode of operation when none of the open loop engine operating conditions exist.

During operation, the MCU causes the [1][2]stepper motor to drive the metering pins to a leaner or richer position in reaction to the voltage input from the oxygen sensor. The stepper motor drives two moveable air metering pins in the carburetor to control the air/fuel ratio.

The engine operating characteristics almost never allow the MCU to compute a single metering pin position that constantly provides the optimum air/fuel mixture. Therefore, the closed loop operation is characterized by the constant movement of the metering pins because the MCU is constantly making corrections to the air/fuel mixture in an attempt to create an optimum air/fuel mixture ratio.