Abstract: In an engine exhaust emission control system, a ternary catalyst and a hydrocarbon adsorber are provided in an exhaust passageway from an engine. The ternary catalyst includes first passages through which an exhaust gas discharged from the engine flows, and second passages through which the exhaust gas which has flowed through the first passages and the hydrocarbon adsorber flows. The first and second passages are laminated to each other to enable heat exchange therebetween. The hydrocarbon adsorber is capable of being cooled by a cooling medium. Thus, it is possible to reliably prevent hydrocarbons in the exhaust gas from being released to the atmosphere during the cold start of the engine.

Abstract: An exhaust gas-purging system for an internal combustion engine includes a catalyst arranged in an exhaust passage of the engine, for purifying exhaust gases emitted from the engine. The system detects an engine operating condition and a catalyst temperature parameter indicative of the temperature of the catalyst. The supply of secondary air to the exhaust passage and the flow path cross-sectional area of the exhaust passage are controlled based on at least one of the operating condition of the engine and the catalyst temperature parameter.

Abstract: An exhaust gas-purifying system for an internal combustion engine is provided with hydrocarbon-adsorbing catalyzer for adsorbing unburnt gas components present in exhaust gases. At least one exhaust gas-purifying catalyzer is arranged in the exhaust passage at a location downstream of the hydrocarbon-adsorbing catalyzer. A bypass passage bypasses the hydrocarbon-purifying catalyzer. A changeover valve is arranged in the exhaust passage at a branchpoint between the bypass passage and the exhaust passage, for selecting a first flow path in which exhaust gases are guided to the unburnt gas component-adsorbing catalyzer, or a second flow path in which exhaust gases are guided through the bypass passage. First and second exhaust gas concentration sensors are arranged in the exhaust passage at locations upstream and downstream of the hydrocarbon-purifying catalyzer.

Abstract: A secondary air supply control system for an internal combustion engine having at least one catalyst arranged in the exhaust system comprises an electric air pump for supplying secondary air to the exhaust system at a location upstream of the catalyst, and a catalyst temperature sensor for detecting the temperature of the catalyst. The ECU calculates a rate of variation in the temperature of the catalyst detected by the catalyst temperature sensor per a predetermined time interval, and controls an amount of secondary air to be supplied by means of the electric air pump, in response to the calculated rate of variation in the temperature of the catalyst.

Abstract: A catalyst deterioration-determining system determines deterioration of a catalyst arranged in the exhaust passage of an internal combustion engine. An ECU is responsive to an output from an O.sub.2 sensor arranged upstream of the catalyst or outputs from O.sub.2 sensors arranged upstream and downstream of the catalyst for controlling the air-fuel ratio of a mixture supplied to the engine by means of an air-fuel ratio correction value (first air-fuel ratio control). When the engine is in a predetermined operating condition, the system effects changeover from the first air-fuel ratio control to a second air-fuel ratio control which is responsive to the output from the downstream O.sub.2 sensor for controlling the air-fuel ratio of the mixture by means of the air-fuel ratio correction value.

Abstract: A catalytic converter heater control system for an internal combustion engine comprising a catalytic converter installed in the engine exhaust gas passage and having a small capacity section on its upstream side and a large capacity section on its downstream side. The system has a pair of oxygen sensors installed one on the upstream side and one on the downstream side of the catalytic converter, a heater installed on the small capacity reaction section for heating incoming exhaust gas, and an electronic control unit for operating the heater when the difference between the outputs of the oxygen sensors is smaller than a prescribed value.