Air-fuel ratio controller for internal combustion engine

Abstract

An air-fuel ratio controller for an internal combustion engine, which controller is capable of: properly correcting an air-fuel ratio after a start-up explosion; preventing inconveniences such as occurrence of an engine stall, a decrease in an engine rotational speed, and a discharge of exhaust gases containing harmful components; and, allocating an idle time-learning value with reference to a rotational engine speed that is obtained at the time of engine start-up, thereby enhancing convenience of use. To this end, the air-fuel ratio controller is provided with an additional feature whereby it is determined, in executing a rotational engine speed-determining item of an idle time-learning region condition, that the rotational engine speed-determining item is satisfied when a rotational engine speed is equal to or less than a value obtained by addition of an ISC target rotational speed and a predetermined value, the predetermined value including either a fixed value or a variable value, the variable value being mapped on a table for each water temperature.