Abstract: When fully closed throttle opening learning device M1 learns a fully closed throttle opening value THMIN on the basis of an actual throttle opening value TH at an idle running time, comparison device M2 compares the sum of the fully closed throttle opening value THMIN and a predetermined value a with the actual throttle opening value TH to decide the possibility of the occurrence of a fault, and fault decision acceptance device M3 decides the acceptance/rejection of execution of the fault decision of an idle revolution controlling unit IC on the basis of the comparison result of the comparison device M2. As a result, even with a degradation in the output characteristics of a throttle opening sensor, an erroneous decision can be avoided by rejecting the execution of the fault decision when there is a possibility of an erroneous decision.

Abstract: An evaporative fuel control system for an internal combustion engine having a throttle valve arranged in the intake system. A canister adsorbs evaporative fuel generated in the fuel tank. A purging passage extends between the canister and the intake system, for purging evaporative fuel into the intake system at a location downstream of the throttle valve, and a purge control valve is arranged across the purging passage, for controlling the flow rate of evaporative fuel supplied to the intake system through the purging passage. When the engine is in a predetermined operating condition, the flow rate of evaporative fuel supplied to the engine is changed by controlling the purge control valve, then the degree of influence of the evaporative fuel on an air-fuel ratio of a mixture supplied to the engine is detected before and after the changing of the flow rate of the evaporative fuel, and an operating error of the purge control valve is determined based on the detected degree of influence.

Abstract: An evaporative fuel-processing system for an internal combustion engine includes a canister for adsorbing evaporative fuel generated in the fuel tank, a charging passage connecting between the canister and the fuel tank, a purging passage connecting between the canister and the intake system of the engine, an open-to-atmosphere passage for communicating the canister with atmosphere, a charge control valve for selectively opening and closing the charging passage, a purge control valve for selectively opening and closing the purging passage, and a vent shut valve for selectively opening and closing the open-to-atmosphere valve, and a pressure sensor inserted in the charging passage at a location on one side of the charge control valve closer to the fuel tank, for detecting internal pressure within the charging passage. When predetermined conditions are satisfied, the purge control valve is closed and the charge control valve and the vent shut valve are opened.

Abstract: An air-fuel ratio sensor deterioration-detecting system is provided for an internal combustion engine having first and second air-fuel ratio sensors arranged in the exhaust system upstream and downstream of a catalytic converter therein. An ECU calculates a control parameter, based on an output from the second air-fuel ratio sensor, calculates an air-fuel ratio correction amount, based on an output from the first air-fuel ratio sensor and the calculated control parameter, and executes air-fuel ratio feedback control, based on the calculated air-fuel ratio correction amount.

Abstract: An air-fuel ratio control system for an internal combustion engine has an exhaust gas component concentration sensor having a sensor element and arranged in the exhaust system of the engine, for detecting concentration of a predetermined component present in exhaust gases emitted from the engine. An ECU controls the air-fuel ratio of an air-fuel mixture supplied to the engine, based on results of comparison between an output value from the sensor and a predetermined reference value, and detects deterioration of the exhaust gas component concentration sensor, based on the output value from the sensor. Engine operating condition sensors detect operating conditions of the engine. It is determined whether or not the engine is in a predetermined engine operating condition in which the sensor element temperature of the exhaust gas component concentration sensor lowers, based on outputs from the engine operating condition sensors.

Abstract: An ignition timing control system for vehicle internal combustion engines which retards the ignition timing during acceleration so as to reduce power shock caused by drive shaft vibration generated when the body of a vehicle with a high-powered engine is not able to keep up with the sudden change in engine output torque and so as to avoid the combustion knock that is apt occur during acceleration. In order to compensate for the monifold pressure lag when an acceleration state is detected, the engine load is monitored as to whether it reaches a reference level within prescribed a period, and only after it is confirmed that the engine output torque has actually begun to increase within the prescribed period, the ignition timing retard is commenced. The retarded ignition timing is maintained for another period when the engine load is above a second reference level and then returned in the advance direction at a first slow rate.

Abstract: A method of controlling exhaust gas recirculation for an internal combustion engine having an exhaust gas recirculation control system comprises the step of determining that there is failure in the exhaust gas recirculation control system when a difference between an actual value of valve opening of an exhaust gas recirculation valve of the system arranged in an exhaust gas recirculation passage for controlling an amount of exhaust gases returned from an exhaust passage to an intake passage of the engine and a desired value of the valve opening of the exhaust gas recirculation valve is equal to or larger than a predetermined value which is dependent on operating conditions of the engine.