Air-fuel ratio control system

Claim 1

In an air-fuel ratio control system for an internal combustion engine having an intake passage, fuel supply means for supplying fuel to cylinders of the engine through the intake passage in dependency on engine operating conditions, an exhaust passage from the engine, an O 2 -sensor for detecting the concentration of oxygen in exhaust gases passing through the exhaust passage, an electronic feedback control circuit comprising a comparator for comparing an output signal of the O 2 -sensor, control circuit means responsive to an output of the comparator to produce a control signal, and a driving circuit responsive to the control signal for driving the fuel supply means and for controlling air-fuel ratio in the intake passage to a value approximately equal to a stoichiometric air-fuel ratio, the improvement comprising coolant temperature sensor means for producing a temperature signal dependent on temperature of coolant of the engine, first detecting means for detecting rapid acceleration and deceleration respectively of the engine for producing an engine operation signal, comparing means for comparing the temperature signal with a lower temperature and a higher temperature, respectively, for producing a first signal when the coolant temperature is lower than the lower temperature and for producing a second signal when the coolant temperature is lower than said higher temperature, first means responsive to said first signal of said comparing means for producing a feedback control interrupting signal for rendering said electronic feedback control circuit inoperative, and said first means responsive simultaneously to the second signal and to the engine operation signal for producing said feedback control interrupting signal for rendering said electronic feedback control circuit inoperative.