Abstract: Methods and systems for diagnosing a multiple cylinder engine are provided herein. An exemplary method of diagnosing an internal combustion engine system having a multi-cylinder internal combustion engine is described. In one example, cylinder air-fuel imbalance is determined from the squared value of a difference of two values.

Abstract: Methods and systems for diagnosing a multiple cylinder engine are provided herein. An exemplary method of diagnosing an internal combustion engine system having a multi-cylinder internal combustion engine is described. In one example, cylinder air-fuel imbalance is determined from the squared value of a difference of two values.

Abstract: The present invention provides a malfunction diagnostic apparatus for an evaporated fuel purge system in an internal combustion engine, capable of detecting abnormalities such as looseness or clogging in the purge line between a purge valve and an engine intake passage. An electric pump 14 is turned on when a purge valve 5 is in a closed state and a selector valve 20 is in an open state. After the lapse of a given time period Tref, a load-current initial value I1 of the electric pump 14 is detected at the moment switching the selector valve 20 to a closed state. After the lapse of a given time period Tpump, the purge valve 5 is switched to an open state, and a load-current final value at the moment after the lapse of a given time period Tpurge. As in the curve A, when a load current final value I2A is equal to or less than the load current initial value I1, it is determined that the gaseous communication state in the purge line between the purge valve 5 and the intake passage is normal.

Abstract: The present invention provides a malfunction diagnostic apparatus for an evaporated fuel purge system in an internal combustion engine, capable of detecting abnormalities such as looseness or clogging in the purge line between a purge valve and an engine intake passage. An electric pump 14 is turned on when a purge valve 5 is in a closed state and a selector valve 20 is in an open state. After the lapse of a given time period Tref, a load-current initial value I1 of the electric pump 14 is detected at the moment switching the selector valve 20 to a closed state. After the lapse of a given time period Tpump, the purge valve 5 is switched to an open state, and a load-current final value at the moment after the lapse of a given time period Tpurge. As in the curve A, when a load current final value I2A is equal to or less than the load current initial value I1, it is determined that the gaseous communication state in the purge line between the purge valve 5 and the intake passage is normal.

Abstract: A system for diagnosing evaporation control system failures repeatedly introduces pressure, positive or negative, into the evaporation control system and closes up it hermetically, a plurality of times (for example two times), and detects changes in internal pressure in the evaporation control system. An average value of the internal pressure changes is compared to a threshold value so as to judge whether there is leakage of fuel vapors of the evaporation control system. When a difference between the internal pressure change is greater than a specified value, the evaporation control system failure diagnosis is interrupted.

Abstract: The invention relates to an apparatus for diagnosing thermostat trouble in an engine cooling system comprising a thermostat which works to open a valve to make a cooling water flow through a radiator when the cooling water temperature for an engine becomes more than a predetermined temperature, or to close the valve to make the cooling water bypass a radiator when this temperature becomes less than the predetermined temperature. The apparatus comprises means for calculating a radiation heat amount from a radiator received by the cooling water for the engine and means for determining whether the thermostat trouble has occurred based on the radiation heat amount calculated by the means for calculating the radiation heat amount.

Abstract: A valve operation verifying system for making verification of valve operation of an EGR valve of a type having a diaphragm elastically deformable according to operating conditions of an engine to admit controlled amounts of exhaust gas that is recirculated into an intake air stream which verifies, on a basis of gas pressure in an EGR passage, whether the diaphragm remains elastically deformable as specified and whether a pressure sensor remains free from freezing, and executes the verification of valve operation of the EGR valve on a basis of a change in the gas pressure in the EGR passage when the EGR valve opens and when it closes, and when the temperature of ambient air is lower than a critical point, verifying that the diaphragm remains elastically deformable as specified and that said pressure sensor is free from freezing.

Abstract: A leakage diagnostic system for making a judgement of leakage of a fuel purge system, which has in order from the side of a fuel tank a control valve, a canister and a purge valve disposed in a purge passage and a relief valve isolating the canister from the atmosphere, based on a rising rate of pressure in the purge passage between the fuel tank and the intake system isolated from the atmosphere after lowering and keeping the interior of the purge passage below specified negative pressure level for a specified period of time. When the interior of the fuel tank increases above a threshold level after a specified period of time, the leakage diagnostic system delivers a judgement of leakage of the purge system.

Abstract: A catalyst degradation determination apparatus having O.sub.2 sensors provided at the upstream and downstream of a catalyst, detects degradation of the catalyst by, during A/F ratio feed-back control since an engine has been started, comparing an integrated value of output values from the upstream O.sub.2 sensor with that of output values from the downstream O.sub.2 sensor. Upon starting integration of the output values from the respective O.sub.2 sensors, change of activated status of the catalyst is judged. If the status of the catalyst is approximately the same as a previous status, the integration is started with previous integrated values. On the other hand, if the status of the catalyst is different from the previous status, the previous integrated values are reset, and the integration of the output values from the respective O.sub.2 sensors is started from the beginning. This prevents erroneous catalyst degradation determination.

Abstract: A lean burn engine adapted to establish a specified air-fuel ratio leaner by predetermined rate than a stoichiometric air-fuel ratio in a range of low engine speeds and low engine loads is provided with an air intake system of a low speed type which provides a high charging efficiency in a range of low engine speeds and an exhaust system capable of eliminating a nitrogen oxide emission in the exhaust even during lean burning.

Abstract: An engine control system computes an average value for an air-to-fuel feedback control based on which the amount of fuel vapors trapped in a canister, a purge air flow rate on the basis of a pressure difference between before and after a canister purge valve and a duty ratio at which the canister purge valve is activated, the amount of purged fuel vapors on the basis of the estimated trapped fuel vapor amount and purge air flow rate based on which the amount of fuel vapors entering into the combustion chamber. During execution of a canister purge, the purged gas flow rate is gradually varied toward a target rate so as to prevent the air-to-fuel feedback control from encountering disturbances.

Abstract: A fuel injection control system for controlling fuel delivery a necessary amount of fuel according driving conditions through at least leading and trailing fuel injections for each of cylinders every cycle in a specified range of driving conditions and executes fuel cut-off control according to a fuel cut-off pattern upon an occurrence of a demand for an engine torque drop starts said fuel cut-off control from when injection timing for leading fuel injection of a cylinder is reached first after the occurrence of the torque drop command.

Abstract: An air-fuel ratio control system for an engine for controlling an amount of a fuel mixture to be delivered into a combustion chamber so that an air-fuel ratio of the fuel mixture attains a target air-fuel ratio performs selecting one of a plurality of predetermined target air-fuel ratios according to engine operating conditions, controlling an amount of a fuel mixture so as to attain a selected target air-fuel ratio, and changing a speed at which the target air-fuel ratio is changed from one to another ratio higher with an increase in deviation of the other target air-fuel ratio from the one target air-fuel ratio.

Abstract: An anti-vehicle-thief apparatus having an immobilizer unit for comparing a specific first code received from a transponder to a stored code just after an engine is started, and when these codes are identical, outputting a second code to an EGI unit, the EGI unit for comparing the second code to a stored code, and when these codes are identical, permitting the engine to continue operation, a CPU for counting the number of times that an ignition switch power supply is turned ON and OFF during a code comparison time period, and backup RAM capable of storing the counted number of times that the ignition switch power supply is turned ON and OFF for a predetermined time period. When the ignition switch power supply is turned ON and OFF repeatedly more than a predetermined number of times, the EGI unit causes the engine to stop.

Abstract: An alternator control system controls a field current passing an alternator so as to regulate a terminal voltage of a vehicle battery to a target voltage, based on a deviation of the terminal voltage from the target voltage, by feedback control. The field current is corrected based on a delay in current generation of the alternator.

Abstract: An air-fuel control system for a lean burn engine which carries out lean burning under specific engine operating conditions causes the engine to burn at an stoichiometric air-fuel ratio regardless of engine operating conditions upon an occurrence of malfunctions of a stratifying device and/or a fuel injection timing control device, so as thereby to enable the engine always to operate in good conditions.

Abstract: A fuel system for feedback controlling an air-to-fuel ratio to maintain an ideally combustible air-fuel mixture includes an evaporation control device, which stores fuel vapors from a fuel tank and purges the fuel vapors stored therein into an intake system, and a fuel vapor evaluation system, which calculates an average of the feedback control parameters, estimates an amount of the fuel vapors stored in the evaporation control means based on the average feedback control parameter, calculates an amount of the fuel vapors replenished into the intake system based on the estimated amount of fuel vapors, and calculates a difference between an amount of fuel necessary for an ideally combustible air-fuel mixture and the replenished amount of fuel vapors. Fuel in an amount equal to the difference is delivered into the intake system.

Abstract: A fuel injection control system for an engine includes fuel injection valves, each of which injects fuel to one cylinder a plurality of times during each cycle. The system has an arithmetic device for calculating a required fuel injection amount based on driving conditions and a trailing side injection capability of a trailing side injection time point, a determination device for comparing the required fuel injection amount with the trailing side injection capability and determining which is greater, and a fuel injection controller for setting a leading side injection time point and a trailing side injection time point and setting a leading side injection amount and a trailing side injection amount.

Abstract: An ignition timing control system for an engine equipped with an automatic transmission corrects an ignition timing advance so as to retard ignition upon a demand to drop engine output torque when resumption of fuel injection is required after it has been interrupted during deceleration or when a shift of the automatic transmission is required. The ignition timing advance is corrected by a decaying retardation value so as to gradually fall with the passage of time. The corrected ignition timing advance is kept above a specific lower ignition timing advance limit, which is set smaller for lower air charging levels than for higher air charging levels. The corrected ignition timing advance is also kept below a specific lower limit ignition timing advance, which is set larger for lower air charging levels than for higher air charging levels.

Abstract: A fuel control system for an engine has a fuel injector which injects fuel into an intake passage communicating with a combustion chamber. The quantity of a direct delivery part of fuel injected from the fuel injector which is directly fed to the combustion chamber is estimated, the quantity of a drawn part of fuel which has been on a wall surface of the intake passage and is vaporized and fed to the combustion chamber together with the direct delivery part is estimated, and the quantity of fuel to be injected from the fuel injection means is dcetermined on the basis of the estimated quantities of the direct delivery part and the drawn part so that the sum of them provides a desired quantity of fuel to be fed to the combustion chamber. The estimated quantity of at least one of the direct delivery part and the drawn part is increased as a factor which governs the degree of evaporation of the fuel on the wall surface changes in such a direction as to promote evaporation of the fuel on the wall surface.