Engine control system having exhaust gas sensor

Abstract

An internal combustion engine including an intake system for providing a supply of intake gas to the engine, an exhaust system for exhausting combustion gas from the engine as exhaust gas and an engine control system. The engine control system includes an exhaust gas sensor provided in the exhaust system of the engine for producing an electric signal which corresponds to the concentration of a constituent in the engine exhaust gas, a regulating device for regulating at least one of factors which affects operating conditions of the engine, and a control circuit which includes a comparator for comparing the electric signal with a first reference value to produce a control signal, a discriminating circuit including an operation circuit for performing operations to obtain rate of change in a unit time of the electric signal and produce a sensor activated signal when the rate of change of the electric signal is greater than a second predetermined value and a signal holding circuit for holding the sensor activated signal until the engine is stopped, a gate circuit responsive to the sensor activated signal applied from the signal holding circuit and allowing to pass the control signal from the comparator to the regulating device to control the regulating device under the control signal.