DISPOSITIF DE COMMANDE PAR REACTION DU RAPPORT AIR-CARBURANT, CONCU POUR PERMETTRE UN FONCTIONNEMENT STABLE DU MOTEUR DANS DES CONDITIONS DE FONCTIONNEMENT PARTICULIERES

An air/fuel ratio feedback control system adapted to control the air/fuel ratio of an air/fuel mixture being supplied to an internal combustion engine, by the use of a first coefficient having a value variable in response to actual exhaust gas concentration and at least one second coefficient having a value variable in dependence on the kind of a particular operating condition or region in which the engine is operating. The control system is operable such that when the engine is operating in an operating condition other than predetermined particular operating conditions of the engine, the value of the first coefficient is varied in response to the output of an exhaust gas concentration sensor, and simultaneously the value of the second coefficient is held at a first predetermined value, and when the engine is operating in one of the predetermined particular operating conditions, the value of the second coefficient is held at a second predetermined value, and simultaneously the value of the first coefficient at a third predetermined value which is a mean value of values of the first coefficient obtained when the engine is operating in the above operating condition other than the particular operating conditions.