Abstract: An exhaust gas recirculation system for returning part of exhaust gas of an engine to an intake system has at least one EGR gas introduction port for directing the EGR gas into an intake air passage downstream of a throttle valve. The EGR introduction port opens, into the intake passage, in a tangential direction to produce a circumferential flow along an inside curved surface of the intake air passage around a central back flow region behind the throttle valve to mix the EGR gas efficiently with the fresh intake air and to prevent deposits on the throttle valve.

Abstract: A fuel delay correction under transient engine running conditions is separated into a short-term delay correction and a long-term delay correction, and the fuel injection amount is corrected by respectively applying these correction according to the engine running conditions. A basic updating amount of these corrections is computed based on the difference between an air-fuel ratio which is actually detected and a target value of the air-fuel ratio, and the basic updating amount is separated into an updating amount for the short-term delay correction and an updating amount for the long-term delay correction by an assignment factor which is based on the temperature of a part of the intake air passage to which injected fuel adheres. The respective correction amount is updated by the assigned updating amount, and stored in a memory.