Abstract: A system is provided with a sensor for sensing the vibration of the engine, and control means responsive to an output of the sensor at a condition of knocking in the engine and for producing a knock signal. A control means is provided responsive to the knock signal for enriching the air-fuel mixture supplied to the engine so as to prevent the knocking. The system further comprises an ignition timing control system responsive to the knock signal for retarding the ignition timing.

Abstract: A fuel-vapor emission control system has a canister having a vacuum operated purge control valve, communicated with a float chamber of a carburetor and a fuel tank for purging fuel-vapor. A vacuum chamber of the vacuum operated purge control valve is communicated with a port provided in the carburetor so as to apply manifold vacuum to the vacuum chamber at partial-throttle operation. Parallel purge lines are provided for communicating the canister with an intake manifold of the engine. A solenoid operated valve is provided in one of the purge lines for controlling the purging of the fuel-vapor. The solenoid operated valve is opened for the purging by a signal from a vehicle or engine speed sensor under such conditions that the engine does not stall.