Control system for internal combustion engine equipped with exhaust gas purifying catalyst

摘要

A control system for an internal combustion engine equipped with a catalytic converter including an exhaust gas purifying catalyst. The control system comprises a catalyst deterioration diagnosing device for diagnosing the deterioration condition of the catalyst. The operation of the catalyst deterioration diagnosing device is avoided when a first frequency at which an engine operating condition shifts to a range for stopping fuel supply to a fuel injector valve becomes larger by not less than a predetermined value than a second frequency at which the engine operating condition shifts to a range for increasing the amount of the fuel supply, thereby preventing the catalyst deterioration diagnosis from being carried out under a condition in which the catalyst is subjected to a high temperature and lean (air-fuel ratio) atmosphere.