Abstract: An exhaust purifying system for an automobile engine including an exhaust system for the emission of exhaust gases to the atmosphere through a catalytic converter. The system comprises a temperature detector for detecting a signal indicative of the temperature of the catalyst, a total engine operating hour detector for detecting a signal indicative of the total operating hour over which the engine has been operated, a spark timing control for retarding the spark timing when the temperature detector detects that the catalyst temperature is lower than a predetermined value, and a retard time corrector for increasing the amount of control to be performed by the spark timing control with increase within a predetermined range detected by the total engine operating hour detector.

Abstract: An internal combustion engine has an intake system provided with a valve for controlling the intake air flow in an idling operation. There is provided a control system including an engine speed detector and a control circuit which compares the engine speed signal from the engine speed detector with a reference value corresponding to a desired idling speed to produce a feedback signal for adjusting the valve. There is also provided an external load detector for producing a modifying signal when an external load is applied to the engine in the idling operation. The control system functions to interrupt the feedback control under the feedback signal for a predetermined time when the external load is applied or removed so as to stabilize the engine speed in a transient period.