Abstract: An exhaust gas purifying apparatus for an internal combustion engine, including a particulate filter provided in an exhaust passage of the engine; a pressure difference sensor for detecting a pressure difference between upstream and downstream side pressures of the particulate filter; an upstream side passage, which connects the pressure difference sensor and an upstream side with respect to the particulate filter of the exhaust passage; and a downstream side passage, which connects the pressure difference sensor and a downstream side with respect to the particulate filter of the exhaust passage. An exhaust gas flow rate is calculated according to an operating condition of the engine. A characteristic of change in the pressure difference, which is detected by the pressure difference detector and corresponds to a change in the exhaust gas flow rate, is detected. An abnormality of the downstream side passage is determined based on the characteristic of change in the pressure difference.

Abstract: An exhaust gas purifying apparatus for an internal combustion engine, including a particulate filter provided in an exhaust passage of the engine; a pressure difference sensor for detecting a pressure difference between upstream and downstream side pressures of the particulate filter; an upstream side passage, which connects the pressure difference sensor and an upstream side with respect to the particulate filter of the exhaust passage; and a downstream side passage, which connects the pressure difference sensor and a downstream side with respect to the particulate filter of the exhaust passage. An exhaust gas flow rate is calculated according to an operating condition of the engine. A characteristic of change in the pressure difference, which is detected by the pressure difference detector and corresponds to a change in the exhaust gas flow rate, is detected. An abnormality of the downstream side passage is determined based on the characteristic of change in the pressure difference.

Abstract: A failure diagnosis apparatus for a temperature sensor which detects a temperature that changes depending on an operating condition of an internal combustion engine. Determining that the temperature sensor fails, if the execution condition of the failure determination is satisfied and a temperature difference between the maximum temperature and the minimum temperature detected by the temperature sensor in the determination period, is less than a failure determination threshold value, when the starting of the engine in the preceding engine operation cycle was a cold start.

Abstract: A failure diagnosis apparatus for a temperature sensor which detects a temperature that changes depending on an operating condition of an internal combustion engine. Determining that the temperature sensor fails, if the execution condition of the failure determination is satisfied and a temperature difference between the maximum temperature and the minimum temperature detected by the temperature sensor in the determination period, is less than a failure determination threshold value, when the starting of the engine in the preceding engine operation cycle was a cold start.

Abstract: A failure diagnosis apparatus for diagnosing a failure in an evaporative fuel processing system is disclosed. The evaporative fuel processing system has a fuel tank, a canister containing an adsorbent for adsorbing evaporative fuel generated in the fuel tank, an air passage connected to the canister and communicating with the atmosphere, a first passage for connecting the canister and the fuel tank, a second passage for connecting the canister and an intake system of an internal combustion engine, a vent shut valve for opening and closing the air passage, and a purge control valve provided in the second passage. The purge control valve and the vent shut valve are closed when stoppage of the engine is detected and it is determined whether there is a leak in the evaporative fuel processing system according to the detected pressure in the evaporative fuel processing system during a predetermined determination time period after closing the purge control valve and the vent shut valve.

Abstract: A failure diagnosis apparatus for diagnosing a failure in an evaporative fuel processing system is disclosed. The evaporative fuel processing system has a fuel tank, a canister containing an adsorbent for adsorbing evaporative fuel generated in the fuel tank, an air passage connected to the canister and communicating with the atmosphere, a first passage for connecting the canister and the fuel tank, a second passage for connecting the canister and an intake system of an internal combustion engine, a vent shut valve for opening and closing the air passage, and a purge control valve provided in the second passage. The purge control valve and the vent shut valve are closed when stoppage of the engine is detected and it is determined whether there is a leak in the evaporative fuel processing system according to the detected pressure in the evaporative fuel processing system during a predetermined determination time period after closing the purge control valve and the vent shut valve.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an ECU which cuts off fuel supply to the engine at deceleration thereof, measures a fuel cut-off period over which the fuel cut-off means cuts off fuel supply to the engine, and enriches the air-fuel ratio of a mixture supplied to the engine to a degree dependent upon the measured fuel cut-off period, at the restart of fuel supply to the engine immediately after termination of cutting-off of fuel supply to the engine.

Abstract: Supply of fuel is stopped when fuel pressure sensed by a pressure sensor provided upstream of a regulator is at a predetermined value or less to avoid abnormal combustion caused by improper adjustment of air/fuel ratio. Even slight variation of the fuel pressure is sensed by monitoring the fuel pressure in an interval after closing a fuel shut-off valve once opened to re-opening of it. In addition, an abnormal state in the fuel system is detected by comparing an accumulated value of amount of injected fuel and an estimated value of fuel consumption in the tank. Furthermore, the peak current value of the fuel injection valve is controlled so that, when the engine at a low temperature is started, lift load of the injection valve is larger than sticking force of the injection valve, thereby preventing such situation where the injection valve is frozen so that it cannot supply fuel to the engine. In this case, the engine can be smoothly started by simultaneously controlling the valve open time.