AIR-FUEL RATIO CONTROLLING METHOD FOR INTERNAL-COMBUSTION ENGINE

PURPOSE:To keep excellent exhaust-gas purifying characteristics of an engine, by executing open-loop control of the air-fuel ratio when the temperature of cooling water is lower than a feedback control starting temperature, and controlling the temperature of cooling water according to the engine load. CONSTITUTION:In operation of an engine 4, it is judged at first by a control circuit 16 whether activation of an O2-sensor 14 is completed. In case that the judgement is YES, a temperature TW01 for starting feedback control of the cooling-water temperature is searched from a map. Here, the temperature TW01 is set at either of two reference temperatures TW1, TW2 by using a prescribed vehicle speed Vcr as a threshold value. Then, judgement is made whether the temperature TW detected by a water-temperature sensor 12 is higher than the temperature TW01, and in case of TWTW01, on the other hand, the injector 15 is controlled by way of feedback control when other operational conditions requiring open-loop control of the cooling-water temperature are not satisfied.