Air-fuel ratio control system for internal combustion engines

摘要

An air-fuel ratio control system for an internal combustion engine includes an ECU which cuts off fuel supply to the engine at deceleration thereof, measures a fuel cut-off period over which the fuel cut-off means cuts off fuel supply to the engine, and enriches the air-fuel ratio of a mixture supplied to the engine to a degree dependent upon the measured fuel cut-off period, at the restart of fuel supply to the engine immediately after termination of cutting-off of fuel supply to the engine. When a second cutting-off of fuel supply to the engine is carried out within a predetermined time period after the restart of fuel supply to the engine immediately after termination of a first cutting-off of fuel supply to the engine, the ECU sets the degree of enriching the air-fuel ratio of the mixture supplied to the engine according to the sum of a first fuel cut-off period over which the first cutting-off of fuel supply to the engine lasted and a second fuel cut-off period over which the second cutting-off of fuel supply to the engine lasted.