Abstract: In apparatus and method for diagnosing an EGR (Exhaust Gas Recirculation) system in an internal combustion engine, a combustion time duration (MT) in one combustion stroke is measured, the combustion time duration including at least an approximately combustion end period, a predictive (reference) combustion time duration (MTA) in one combustion stroke is derived on the basis of engine driving condition and a target EGR rate to be carried out by the EGR system, and the measured combustion time duration (MT) is compared with the predictive (reference) combustion time duration (MTA). Depending on a result of the comparison, the diagnosing apparatus and method determine whether a failure in the EGR system occurs.

Abstract: In order to improve the accuracy in detection of a crank angle position of an internal combustion engine, the crank angle position obtained from signals from a crank angle sensor is corrected by using a cylinder pressure inside an engine cylinder sensed by a cylinder pressure sensor. While the engine is in a predetermined non-firing condition, a control unit determines a crank angular distance (A at steps S1.about.S12) from a reference crank angle position at which the crank angle sensor produces a reference angle signal (REF), to a top dead center indicative position at which the sensed cylinder pressure becomes maximum. The control unit calculates a deviation (.DELTA.REF) of the determined crank angular distance (A) from a predetermined reference angular distance (70.degree., for example), corresponding to a deviation of the mounting position of the crank angle sensor. Then, the control unit determines a corrected crank angle position (CAA) by using the thus-obtained angular deviation (.DELTA.REF).

Abstract: Apparatus and method for estimating the temperature of a catalytic converter for automotive engine can be estimated simply and accurately. Specifically, the cooling water temperature Tws at start-up is presumed to correspond to the ambient temperature, and a lost heat amount Tm is estimated based on the cooling water temperature Tws at start-up, and on the vehicle speed VSP. Then, a time integral value STm of the lost heat amount Tm is computed. On the other hand, the engine intake air quantity Q is presumed to correspond to an exhaust quantity, and a received heat amount Tp, which the catalytic converter absorbs from the exhaust, is estimated based on the intake air quantity Q. Then, a time integral value STp of the absorbed heat amount Tp is computed. The time integral value STm is then subtracted from the time integral value STp to obtain a heat amount X retained in the catalytic converter.

Abstract: A combustion condition detecting system of an internal combustion engine, comprises a first device for detecting the pressure in a cylinder of the engine; a second device for setting an integral range in a crankshaft angle in accordance with a rotation speed of the engine; a third device for integrating the pressure within the integral range thereby to derive an integrated value; a fourth device for judging whether or not an abnormal combustion occurs in the cylinder by comparing the integrated value with a reference value; and a fifth device for issuing an alarm when the fourth device judges occurrence of the abnormal combustion. In accordance with the invention, in a lower engine speed side near the idling speed, the integral range is set to appear after a given crankangle position where the pressure in the cylinder exhibits the maximum.

Abstract: A slip condition of a torque converter is learned at a predetermined operating condition with a lock-up mechanism disengaged, and a diagnosis condition (for example a start time or judgement level of the fault diagnosis) used in diagnosing a fault in the lock-up mechanism on the basis of slip conditions of the torque converter which change after issue of a disengage command to the lock-up mechanism, is corrected in accordance with the learned result. As a result, the diagnosis condition which is conventionally set assuming a maximum viscosity for the operating fluid, can be changed to correspond to the actual viscosity of the operating fluid being used.

Abstract: A fuel injection control system for an internal combustion engine equipped with a fuel injection system includes fuel injector valves. The fuel injection control system comprises a control unit for controlling fuel injection for each fuel injector valve. The control unit has a function to control the fuel injection in accordance with a first characteristic required for engine starting before occurrence of an initial explosion in an engine cylinder, and in accordance with a second characteristic required for normal engine operation after occurrence of the initial explosion.

Abstract: Provided is an apparatus for early detecting a volatility of fuel supplied to an engine after engine start, in order to more precisely provide various increasing corrections during air-fuel-ratio control. During increasing-correction (S4) after engine start, a fuel-injection amount delivered to pre-selected one of cylinders is forcibly changed in a stepped manner (S6). Measured (S10) is an elapsed time T from a time (S7) when the injection-amount is changed in a stepped manner to a time (S9) when the integral Pi of a cylinder internal-pressure reflects its variation based on the stepped change in the injection amount. Since a response to a change in an air-fuel ratio is low in case of a heavy-gravity fuel and high in case of a light-gravity fuel, a fuel volatility such as a heavy gravity or a light gravity can be measured (S11) based on a time interval of said elapsed time T.

Abstract: During a predetermined period of time T upon a start of the engine, when low frequency components of a variation in either of an engine revolution speed or combustion pressure are extracted and the extracted low frequency component level is below a predetermined value (.DELTA.Nref or .DELTA.Peref), an ignition timing is retarded up to a limit such that a variation state of either of the engine revolution speed or the combustion pressure is kept at a value below the predetermined value.

Abstract: Engine output fluctuations are detected based on combustion pressure, and a fuel supply quantity amended so that the output fluctuations approach a permissible limit value. The properties of the fuel being used, can be estimated based on the amendment level, using characteristics that the limit air fuel ratio for stable combustion becomes leaner as the fuel being used is more volatile. Then when the fuel being used is volatile, the target air-fuel ratio in the air-fuel ratio feedback control is made leaner, thereby improving fuel consumption and exhaust gas properties.

Abstract: An electronically controlled fuel-supply system for an internal combustion engine, comprises a fuel tank, a fuel pump mounted in the fuel tank, a fuel-injection valve delivering fuel of a fuel-supply amount, based on its valve opening time period, to an engine cylinder, a pressure regulator mounted in the fuel tank and responsive to a first pressure difference between a fuel pressure of fuel pumped and a reference pressure, for regulating the first pressure difference at a predetermined value, an internal-pressure sensor for detecting an internal pressure in the fuel tank, and a boost-pressure sensor for detecting a boost pressure acting on an open end of a nozzle of the fuel-injection valve. The pressure regulator uses the internal pressure as the reference pressure. A control unit is provided for correcting the valve opening time period in accordance with a second pressure difference between the internal pressure and the boost pressure.

Abstract: A control system for a four-cycle internal combustion engine controls a cam drive mechanism for an intake valve such that a cam of the cam drive mechanism maintains a valve open duration of the intake valve at a short valve open duration in response to a shift from engine operation at low speed with low load to engine operation at low speed with high load, and the cam increases the valve open duration of the intake valve in response to a shift from engine operation at low speed with low load to engine operation at low speed with middle load that is higher than the low load but lower than the high load.

Abstract: A fuel vapor control system for an internal combustion engine is constructed so as to first determine a basic purge gas quantity based on an operating condition of the engine, then corrects the basic purge gas quantity in accordance with an altitude at which the engine is located and determines a conclusive purge gas quantity. The conclusive purge gas quantity is determined so as to increase as the altitude becomes higher, whereby the escape of fuel vapor from the intake system of the engine can be prevented with efficiency and assuredness.

Abstract: A value for a quantity of fuel remaining in a fuel tank is stored when a key switch is switched off. Refueling while an engine is stopped is detected when a difference between a remaining fuel quantity value for when the key switch is switched on and the stored remaining fuel quantity value for when switched off is equal to or greater than a predetermined proportion of the stored remaining fuel quantity value for when switched off. When refueling has been carried out, the fuel property is newly detected based on engine operating conditions, while when refueling has not been carried out, the fuel property is considered to be unchanged, and a fuel supply quantity is controlled in accordance with a fuel property for the previous time.

Abstract: An apparatus and method for determining a characteristic of a fuel actually used in a vehicular internal combustion engine. The characteristic of the fuel actually used in the engine is determined on the basis of a fuel supply quantity (.SIGMA.Ti) to the engine during an engine start until an initial stage of an explosion of an air-fuel mixture in any one of engine cylinders and a time duration measured by a timer (Tr) from a time at which the initial explosion has occurred to a time at which a completion of the explosion has occurred.

Abstract: A signal indicating that a road on which a vehicle is travelling is not a rough road is output when a fluctuation frequency of an engine rotational speed and a fluctuation frequency of a combustion pressure are in approximate agreement, and a fluctuation amplitude of an engine rotational speed is greater by a predetermined value or above than a fluctuation amplitude of a combustion pressure. In other cases a signal indicating that the road on which the vehicle is travelling is not a rough road is output. During rough road travel, misfire detection based on engine rotational speed or combustion pressure is inhibited.

Abstract: To detect the volatility of fuel accurately and speedily, a system for an internal combustion engine is arranged to gradually increase only the fuel supply quantity for a specified cylinder, while monitoring a variation of a combustion pressure in the specified cylinder, until the variation exceeds a predetermined level. The amount of fuel increase (such as AFR) obtained at the time the variation exceeds the predetermined level is used as a parameter representing the volatility of the fuel.

Abstract: The air/fuel ratio of an intake mixture of an internal combustion engine becomes excessively rich due to fuel leaked from the fuel injection valve into the intake system during a period from shut-down until restart. To overcome the resultant poor starting, the amount of leakage is estimated based on the engine temperature at shut down, and an elapsed time from shut-down until restart which is determined for example based on a difference between the engine shut-down temperature and the engine temperature at restart. The start-up fuel injection amount or the start-up intake flow rate is then corrected corresponding to this leakage amount.As a result, since a suitable start-up air/fuel ratio can be obtained in spite of fuel leakage from the fuel injection valve into the intake system, good engine starting can be ensured.

Abstract: An air/fuel ratio control system for an internal combustion engine is effective for improving exhaust characteristics and fuel combustion efficiency. Air/fuel ratio control is carried out by monitoring combustion pressure and analyzing variations therein for frequencies indicative of surge torque. Upon detecting of such indications a map selection function selects data maps from memory for controling the air/fuel ratio to be gradually enriched according to a detected amount of surge torque. If the amount of surge torque is within a predetermined basic range, the system is active to perform lean control for reducing the air/fuel ratio such that the engine may always run as lean as possible without incurring torque loss due to an insufficiently rich air/fuel ratio.

Abstract: The present invention relates to the idle speed control of an internal combustion engine. The output torque required for obtaining the target idle speed is computed, the ignition timing correction amount required for obtaining said required output torque and similarly, the auxiliary air flow rate through the auxiliary air control valve bypassing the throttle valve required for obtaining said required output torque are computed. By carrying out these computations simultaneously, the torque correction is carried out in the best possible response speed by the ignition timing control and subsequently, the torque correction by the auxiliary air flow rate control is carried out. Thereby, the response characteristic of idle speed control can be significantly improved.

Abstract: The open and close frequency of an intake control valve 30 for controlling an intake amount at an open and close time proportion, is variably controlled in accordance with engine rotational speed or elapsed time. As a result, during control of fuel vapor treatment, biased supply to a specific cylinder of fuel vapor drawn into the engine from an absorption device 29 is suppressed, so that an averaged air-fuel ratio can be obtained for each cylinder. Therefore, combustion variation between the cylinders can be avoided, the increased engine vibration due to the resultant increase in combustion pressure variation reduced, and the deterioration in exhaust composition and vehicle driving performance can be minimized.