Open Loop Mode

In this mode the air/fuel mixture is set to a predetermined, non-varying setting by the ECU, and is not influenced by the oxygen sensor signals. This occurs during cold operating temperatures or when throttle is closed (idle or deceleration). In "Open Loop" mode, the fuel mixture is set by the ECU.

Fig 1: 2.3L Feedback Carburetor System Vacuum Schematic

Courtesy of FORD MOTOR CO.

Fig 2: 2.3L Turbo Feedback Carburetor System Vacuum Schematic

Courtesy of FORD MOTOR CO.