AIR-FUEL RATIO CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

PURPOSE:To both maintain the good drivability of an engine and to improve its fuel consumption, by controlling air-fuel ratio of a mixture to a lean state when the engine is in operation with a cooling water temperature in a preset value or more and a throttle opening in a preset degree or less further with a change amount of the throttle opening and a car speed in a predetermined value or less. CONSTITUTION:A control circuit 26, which calculates an intake amount of air on the basis of an intake negative pressure from a vacuum sensor 19 and a detection value from a throttle opening sensor 18 while the basic injection quantity of fuel on the basis of a speed from a distributor 22, performs a correction of various kinds on the basis of detection values from a water temperature sensor 20, O2 sensor 21, car speed sensor 23, etc. That is, a feedback correction by the O2 sensor 21 is suspended when an engine is in operation with its cooling water temperature in a preset value (for instance, 80 deg.C) or more and throttle opening in a preset value (for instance, 50 deg.) or less further with change amounts of a car speed and the throttle opening per a fixed time in a predetermined value or less, and air-fuel ratio is controlled to a lean state by subtracting the basic injection quantity of fuel.