Abstract: A system is described for diagnosing the operation of an exhaust gas recirculation system of an internal combustion engine having a speed density fuel delivery system and having a closed loop fuel adjustment. The EGR system operation is determined by disabling the EGR system and observing the magnitude of change of the integral adjustment of the closed loop system.

Abstract: An air/fuel ratio controller for an internal combustion engine including two memories each having numbers stored at locations addressed by engine operating points with the locations addressed by the engine operating points being updated during closed loop operation in accord with the value of a closed loop adjustment of the air/fuel ratio. Each memory location in the first memory is updated during operation of the engine at the corresponding operating point in accord with an update time constant having a value so that the number stored tracks adjustment value producing the predetermined desired closed loop air/fuel ratio during varying values of engine operating parameters. Each memory location in the second memory is updated during operation of the engine at the corresponding operating point in accord with an update time constant having a value so that the number stored is the average of the values producing the predetermined closed loop air/fuel ratio during varying values of engine operating parameters.

Abstract: An air/fuel ratio controller for an internal combustion engine including a memory having numbers stored at locations addressed by engine operating points with the locations addressed by the engine operating points being updated during closed loop operation in accord with the value of a closed loop adjustment of the air/fuel ratio. Each memory location in the memory is updated during operation of the engine at the corresponding operating point in accord with an update time constant having a value so that the number stored tracks adjustment value producing the predetermined desired closed loop air/fuel ratio during varying values of engine temperature. The update time constant is varied directly with the value of engine temperature so that the rate of adjustment of the numbers in the memory is greater during engine warmup where engine temperature increases rapidly. The memory is used during closed loop operation to preset the closed loop adjustment at least when the engine first operates at an operating point.

Abstract: The idle and main fuel passages of a carburetor are controlled by metering apparatus which is regulated to maintain the idle and part throttle air-fuel mixtures at a selected air-fuel ratio, but during low temperature engine operating conditions the part throttle mixture is leaner than the idle mixture in any particular regulated mode of the metering apparatus. This invention provides a mixture forming assembly which further includes means for leaning the idle mixture only during such low temperature operating conditions; the metering apparatus is then regulated to a rich mode at idle during low temperature engine operating conditions to provide an idle mixture which is leaned to the selected air-fuel ratio, and a lean part throttle mixture is avoided as the throttle is opened from idle to a part throttle position.

Abstract: A closed loop fuel control system is described for a vehicle internal combustion engine which includes an exhaust gas sensor providing a signal having a value determined by the oxidizing/reducing conditions of the exhaust gases. An integral controller is responsive to the output of the exhaust gas sensor and provides a control signal varying in a first direction for sensed oxidizing/reducing conditions greater than a desired condition and varying in an opposite direction for sensed oxidizing/reducing conditions less than the desired condition. A control circuit is responsive to the output of the integral controller to adjust the vehicle engine air/fuel supply device to vary the value of the air/fuel ratio of the mixture supplied to the engine in a direction tending to maintain the desired exhaust gas condition. The output of the integral controller is limited to predetermined values so as to limit the air/fuel ratio control authority of the closed loop circuit.