Abstract: A malfunction detection apparatus for detecting a malfunction in an evaporated fuel purge system in which fuel vapor from a fuel tank is adsorbed in an adsorbent in a canister and the adsorbed fuel vapor in the adsorbent is purged into an intake passage of an engine. The apparatus includes a detection part for detecting a concentration of fuel in the fuel vapor purged into the intake passage so that a change in the detected fuel concentration from a time when a purge cutting is performed to a time when a purging is performed after the purge cutting has been performed is detected, and a discrimination part for determining whether there is a malfunction in the system on the basis of the change in the detected fuel concentration by the detection part.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors disposed on the upstream and the downstream of the catalyst which is installed in the exhaust passage of the engine and has oxygen storage effect, an air-fuel ratio correction amount is calculated in accordance with the output of the upstream O.sub.2 sensor, and the actual air-fuel ratio is adjusted in accordance with the calculated air-fuel ratio correction amount. Further, the determination of the deterioration of the catalyst is carried out in accordance with the output of the second O.sub.2 sensor when the air-fuel ratio of the engine is adjusted.

Abstract: A failure detection device that detects a failure occurring in an evaporative fuel purge system by detecting the pressure inside a vapor passage and a purge passage. The vapor passage and the purge passage are connected via a bypass passage. A pressure sensor is connected to either the vapor passage or the purge passage. An engine control unit is provided which judges that a failure has occurred in the evaporative fuel purge system when the pressure sensor detects a pressure equal to or higher than the predetermined pressure.

Abstract: A rotor with outer teeth is fixed to a crankshaft, a crank angle sensor is disposed facing the outer teeth of the rotor, and the angular velocity of the crankshaft in the power stroke of the cylinders is found from the output pulses of the crank angle sensor. In this case, if the ignition sequence is 1-3-4-2, the angular velocities of the crankshaft for the no. 1 cylinder #1 and the no. 4 cylinder #4 are calculated from the output pulses generated based on the outer teeth of the same region I, while the angular velocities of the crankshaft for the no. 3 cylinder #3 and the no. 2 cylinder #2 are calculated from the output pulses generated based on the outer teeth of the same region II. Therefore, even if there is a manufacturing error in the outer teeth of the region I, so long as no misfire occurs, the angular velocities of the crankshaft will be the same for the no. 1 cylinder #1 and the no. 4 cylinder #4. As opposed to this, if a misfire occurs at the no.

Abstract: A malfunction detection apparatus for detecting a malfunction in an evaporated fuel purge system in which fuel vapor from a fuel tank is adsorbed in an adsorbent in a canister and the adsorbed fuel vapor in the adsorbent is purged into an intake passage of an engine. The apparatus includes a detection part for detecting a concentration of fuel in the fuel vapor purged into the intake passage so that a change in the detected fuel concentration from a time when a purge cutting is performed to a time when a purging is performed after the purge cutting has been performed is detected, and a discrimination part for determining whether there is a malfunction in the system on the basis of the change in the detected fuel concentration by the detection part.

Abstract: An air-fuel ratio control device for an engine having two or more cylinder groups, such as a V-type engine or a horizontally opposed engine, wherein the air-fuel ratio control device controls the air-fuel ratio of cylinder groups in accordance with the output of upstream air-fuel ratio sensors and a downstream air-fuel ratio sensor. The upstream air-fuel ratio sensors are disposed in the individual exhaust passage connected to the respective cylinders upstream of the catalyst converter. The downstream air-fuel ratio sensor is disposed in the common exhaust passage downstream of the catalyst converter. The air-fuel control device usually controls the air-fuel ratios of individual cylinder groups in accordance with the output of the respective upstream air-fuel ratio sensor.

Abstract: In an evaporative emission-control system having a canister for trapping a fuel-vapor evaporated from the fuel tank and a purge control valve for executing a purging, an amount of fuel-vapor trapped in the canister is measured while the engine is stopped or in an idle state. The trapped fuel-vapor is purged from the canister and mixed with an air-fuel mixture when the amount of fuel-vapor trapped in the canister is sufficient for diagnosis while the vehicle is running in a predetermined driving condition. In this purge operation, a concentration of a vapor-laden air from the canister is measured and the occurrence of an abnormal state of the evaporative emission-control system is determined when a change of the concentration of the vapor-laden air after the purging is less than a predetermined value.

Abstract: In an apparatus for diagnosing an abnormality in a fuel injection system in which an injection quantity is feedback-controlled by adjusting a first air-fuel ratio correction value so that an air-fuel ratio is equal to a target air-fuel ratio. The injection quantity is also adjusted by a second air-fuel ratio correction value. When the first air-fuel ratio correction value has reached a first upper limit value, the second air-fuel ratio correction value is set to a second upper limit value. When the first air-fuel ratio correction value has reached a second lower limit value, the second air-fuel ratio correction value is set to a second lower limit value. When the first air-fuel ratio correction value is outside of a predetermined range when a predetermined time has elapsed after the second air-fuel ratio correction value is set to either the second upper limit value or the second lower limit value, it is determined that a fault has occured in the fuel injection system.

Abstract: An apparatus for determining a deterioration of a condition of a three-way catalyst arranged in an exhaust passage of an internal combustion engine, comprising an upstream O.sub.2 sensor arranged in the exhaust passage upstream of the catalyst and a downstream O.sub.2 sensor arranged in the exhaust passage downstream of the catalyst. An air-fuel ratio feedback correction amount is calculated in accordance with the output of the upstream O.sub.2 sensor, and the rate of change of the air-fuel ratio feedback correction amount is decreased when it is determined that the condition of the catalyst has deteriorated.

Abstract: A malfunction detection apparatus for detecting a malfunction in an evaporated fuel purge system for use in an internal combustion engine. The apparatus includes a vapor passage connecting a fuel tank to a canister for feeding fuel vapor from the fuel tank into the canister, a purge passage connecting the canister to an intake passage of the engine for feeding the fuel vapor adsorbed in an adsorbent in the canister into the intake passage, a purge control valve provided for controlling a flow of the adsorbed fuel vapor in the canister being fed into the intake passage, a pressure sensor provided for outputting a signal indicative of pressure in the vapor passage, and a malfunction detection part responsive to the signal outputted by the pressure sensor for detecting a malfunction in the evaporated fuel purge system.

Abstract: Disclosed is an apparatus for detecting abnormality in a secondary air supplier of an engine. The operational status of the engine is monitored by various sensors. When the engine is in a warmed-up state, an electronic control unit (ECU) disables the secondary air supplier to stop secondary air from being supplied to an exhaust manifold. When the engine is in such an operational status in which the secondary air should be supplied, the secondary air supplier is activated and a fuel supplying means is controlled in such a way that a suction air-fuel ratio is forcibly adjusted to a predetermined high value so as to set an exhaust air-fuel ratio low when the secondary air supplier functions properly and set the exhaust air-fuel ratio high when the secondary air supplier is abnormal. When the exhaust air-fuel ratio is detected to be high, the ECU judges the secondary air supplier as abnormal and executes necessary processing, such as outputting an abnormality judgment signal to an external warning device.

Abstract: In a double air-fuel ratio sensor system having three-way catalysts, a full O.sub.2 storage amount of the three-way catalysts is estimated and compared with a predetermined amount. When the estimated full O.sub.2 storage amount is smaller than the predetermined amount, the three-way catalysts are determined to have deteriorated.

Abstract: In a double air-fuel ratio sensor system having two air-fuel ratio sensors upstream and downstream of a catalyst converter, a main air-fuel ratio correction amount is calculated in accordance with the output of the upstream air-fuel ratio sensor, and a sub air-fuel ratio correction amount is calculated in accordance with the output of the downstream air-fuel ratio sensor, thereby adjusting an air-fuel ratio using the two air-fuel ratio correction amounts. When the sub air-fuel ratio correction reaches a lean limit value, an ignition system is determined to be abnormal and a misfire may occur.

Abstract: A device for treating vaporized fuel from a fuel tank of an internal combustion engine, and having a canister. The fuel tank has an inner partition wall which divides the space inside the fuel tank into a first small chamber and a second large chamber, which are separated from each other. A fuel flow is allowed at locations below the fuel levels in the first and second chambers, which are independently connected to the canister device, and a fuel filling pipe is open to the first, small chamber. A pressure control means is provided for maintaining a pressure in the second chamber higher than that in the first chamber, which is near to the atmospheric pressure, whereby fuel vapor is prevented from escaping from the first chamber during a fuel-filling operation.

Abstract: In an air-fuel ratio feedback control system including at least one air-fuel ratio sensor downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is controlled in accordance with the output of the downstream-side air-fuel ratio sensor. When the engine is transferred from an open loop control state such as a fuel cut-off state or an OTP incremental state to an air-fuel ratio feedback control state for a stoichiometric air-fuel ratio by the downstream-side air-fuel ratio sensor, the speed of changing an air-fuel ratio correction amount in accordance with the output of the downstream-side air-fuel ratio sensor is at a conventional speed before the switching of the output of the downstream-side air-fuel ratio sensor, but thereafter (only immediately after the switching of the output of the downstream-side air-fuel ratio sensor or for a predetermined time period), this speed is increased.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is calculated in accordance with the results of the comparison of the outputs of the upstream-side and downstream-side air-fuel ratio sensors with first and second reference voltages, respectively, thereby obtaining an actual air-fuel ratio. The second reference voltage is changed in accordance with the load of the engine, to change the mean air-fuel ratio.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. A center value of an air-fuel ratio correction amount or an air-fuel ratio feedback control parameter calculated based upon the output of the downstream-side air-fuel ratio sensor is calculated by a learning control for regions defined by the period of the output of the upstream-side air-fuel ratio sensor, and an air-fuel ratio feedback control is initiated by using the center value stored for the current region when the engine enters into an air-fuel ratio feedback control state, or when the period of the output of the upstream-side air-fuel ratio sensor is transferred to a different region.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side air-fuel ratio sensor and the downstream-side air-fuel ratio sensor. The adjustment of the air-fuel ratio by the downstream-side air-fuel ratio sensor is stopped when the engine is in a predetermined state.

Abstract: A malfunction detection apparatus for detecting a malfunction in an evaporated fuel purge system for use in an internal combustion engine. The apparatus includes a vapor passage connecting a fuel tank to a canister for feeding fuel vapor from the fuel tank into the canister, a purge passage connecting the canister to an intake passage of the engine for feeding the fuel vapor adsorbed in an adsorbent in the canister into the intake passage, a purge control valve provided for controlling a flow of the adsorbed fuel vapor in the canister being fed into the intake passage, a pressure sensor provided for outputting a signal indicative of pressure in the vapor passage, and a malfunction detection part responsive to the signal outputted by the pressure sensor for detecting a malfunction in the evaporated fuel purge system.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.