Abstract: A catalytic converter is adapted to retard spark timing to increase the temperature of the converter catalyst when a temperature sensor within the converter senses low exhaust temperature. A vacuum advance mechanism is responsive to intake manifold vacuum conducted thereto via an intake vacuum passageway to advance spark timing for the engine. The temperature of exhaust gas from a catalytic converter for exhaust emissions is sensed. When the sensed temperature of the exhaust is below a predetermined value, a comparator outputs an actuation signal which is used to cause a solenoid valve to open an air passageway to admit atmospheric air into the vacuum advance mechanism so that spark timing will be retarded, thereby increasing the temperature of the catalyst.

Abstract: In an internal combustion engine having an intake passage provided therein with a throttle valve for controlling intake flow of air or an air-fuel mixture passing therethrough toward engine cylinders and an exhaust passage, an exhaust gas recirculation system comprises first means for conducting a portion of the exhaust gases from the exhaust passage into the intake passage downstream of the throttle valve and second means provided in the intake passage downstream of the throttle valve for preventing the exhaust gases fed through said first means from flowing upstream toward the throttle valve. Accordingly, the response accuracy of the throttle valve is protected from being impaired due to deposition of exhaust gas contaminants thereon.