Abstract: A misfire detection system and method for a vehicle utilize a controller to obtain a crankshaft speed signal indicative of a rotational speed of an engine crankshaft connected to a device that mitigates vibrational disturbances at the crankshaft caused by misfires of the engine, detect that a first firing event of the engine is a first misfire based on the crankshaft speed signal, monitor a vibrational response of the crankshaft, detect that a consecutive second firing event of the engine is a second misfire based on a first modified crankshaft speed signal and the first set of thresholds, and in response to detecting the second misfire, reset the monitoring of the vibrational response of the crankshaft including modifying the amplitude of the crankshaft speed signal to obtain a second modified crankshaft speed signal and comparing the second modified crankshaft speed signal to a set of thresholds.

Abstract: A misfire detection system and method for a vehicle utilize a controller to obtain a crankshaft speed signal indicative of a rotational speed of an engine crankshaft connected to a device that mitigates vibrational disturbances at the crankshaft caused by misfires of the engine, detect that a first firing event of the engine is a first misfire based on the crankshaft speed signal, monitor a vibrational response of the crankshaft, detect that a consecutive second firing event of the engine is a second misfire based on a first modified crankshaft speed signal and the first set of thresholds, and in response to detecting the second misfire, reset the monitoring of the vibrational response of the crankshaft including modifying the amplitude of the crankshaft speed signal to obtain a second modified crankshaft speed signal and comparing the second modified crankshaft speed signal to a set of thresholds.

Abstract: In a motor vehicle having an engine with an exhaust catalyst and an oxygen sensor upstream of the catalyst and an oxygen sensor downstream of the catalyst, a method for detecting whether the catalyst has aged. Over a test block period of time, the method periodically obtains upstream data points from an oxygen sensor located upstream of the catalyst and from and oxygen sensor located downstream of the catalyst. Absolute differences are calculated between consecutive pairs of the upstream data points and the downstream data points. A ratio between the sums of absolute differences is then calculated, and the ratio is used to determine whether the catalyst has aged.

Abstract: A non-intrusive method and arrangement for detecting the aging of an oxygen sensor, without increasing tailpipe emissions, is provided. The method detects an aging oxygen sensor, located between a motor vehicle engine and a catalytic converter, by sampling a series of oxygen level signals taken over a calibratable time block only when at least one engine operating condition satisfies a predetermined criterion whereunder the method will not intrude upon the engine controller's ability to minimize undesirable exhaust emissions. After a series of signal processing, the samplings are then compared to calibratable thresholds in order to determine the aging degree of the oxygen sensor.

Abstract: A non-intrusive method and arrangement for detecting the aging of an oxygen sensor, without increasing tailpipe emissions, is provided. The method detects an aging oxygen sensor, located between a motor vehicle engine and a catalytic converter, by sampling a series of oxygen level signals taken over a calibratable time block only when at least one engine operating condition. satisfies a predetermined criterion whereunder the method will not intrude upon the engine controller's ability to minimize undesirable exhaust emissions. After a series of signal processing, the samplings are then compared to calibratable thresholds in order to determine the aging degree of the oxygen sensor.

Abstract: In a motor vehicle having an engine with an exhaust catalyst and an oxygen sensor upstream of the catalyst and an oxygen sensor downstream of the catalyst, a method for detecting whether the catalyst has aged. Over a test block period of time, the method periodically obtains upstream data points from an oxygen sensor located upstream of the catalyst and from and oxygen sensor located downstream of the catalyst. Absolute differences are calculated between consecutive pairs of the upstream data points and the downstream data points. A ratio between the sums of absolute differences is then calculated, and the ratio is used to determine whether the catalyst has aged.

Abstract: A method of determining the quality of subsystems of an electronic engine control system is provided. The method monitors an engine parameter representative of a subsystem of interest and compares the parameter to at least one quality limit. The at least one quality limit represents an acceptable performance boundary for a fully functional engine control system. The method then indicates, based on the result of the comparison, whether the subsystem is of satisfactory quality. The method is arranged, without limitation, to determining the quality of start time, start flare, idle control during transmission shift, and speed control.

Abstract: A method of determining the quality of subsystems of an electronic engine control system is provided. The method monitors an engine parameter representative of a subsystem of interest and compares the parameter to at least one quality limit. The at least one quality limit represents an acceptable performance boundary for a fully functional engine control system. The method then indicates, based on the result of the comparison, whether the subsystem is of satisfactory quality. The method is arranged, without limitation, to determining the quality of start time, start flare, idle control during transmission shift, and speed control.

Abstract: A method is provided for monitoring the integrity of a fuel composition sensor in a flexible fueled vehicle. At ignition-on, the fuel composition sensor is tested for electrical and rationality viability. After ignition-on, the fuel composition is periodically, non-intrusively, tested for potential rationality errors. Should the non-intrusive testing indicate that a potential error exists, the fuel composition sensor is intrusively tested for rationality errors. If the intrusive test detects that the fuel composition sensor is malfunctioning, the engine control system converts to a limp-in mode and sets the engine operating parameters based on feedback from an exhaust gas oxygen sensor system.

Abstract: A method is provided for triggering a system for learning the percent alcohol content of a fuel used in a motor vehicle capable of operating on more than one type of fuel. The fuel composition learning system is triggered each time fuel is added to the vehicle's fuel tank, each time the engine is started when the fuel volume in the fuel tank falls below a given value or if a fuel level sending unit malfunction has been detected. The fuel composition learning system is also triggered if an error is detected in the value of the learned percent alcohol content of the fuel.

Abstract: The present invention is directed towards a method of controlling combustion parameters of an internal combustion engine prior to oxygen sensor feedback availability for a flexible fueled vehicle. If the vehicle has previously been running on ethanol or has been using ethanol in the recent past, a first strategy is employed which basis engine fueling on the minimum of a theoretically appropriate fueling value and a theoretically calculated value. If the vehicle has not previously been running on ethanol or has not been using ethanol in the recent past, a second strategy is employed which basis engine fueling on the minimum of the theoretically appropriate fueling value, the theoretically calculated value and a roughness calculated value.

Abstract: The present invention provides a method of compensating for an erroring sensor in a flexible fuel compensation control system for a flexible fueled vehicle. The methodology provides a method for identifying preselected operating conditions without the output of the erroring sensor. As such, the flexible fuel compensation control system may still be employed to ensure vehicle drivability even in the absence of input from an erroring sensor.

Abstract: The present invention provides a method of controlling combustion parameters of an internal combustion engine without a PCV solenoid during a boil-off condition. The methodology detects a boil-off condition and implements one of two modes of boil-off compensation depending on the active status of an inferred alcohol content multiplier update system. The methodology also determines the nature of the air-flow through the internal combustion engine and determines the level of boil-off corruption present and the time when the corruption is complete. After the boil-off condition is determined to be complete, control of the combustion parameters are returned to a normal regime of a flexible fuel compensation system using the inferred alcohol content from the employed mode of boil-off compensation.

Abstract: The present invention provides a flexible fuel compensation system for controlling operating parameters of an internal combustion engine based on a learned value of the percent alcohol content of the fuel using an oxygen feedback system. The methodology determines a fuel composition multiplier based on the percent alcohol content and implements gasoline operating parameters for the internal combustion engine if the fuel composition multiplier is less than a first threshold value, mixed gasoline/alcohol operating parameters if the fuel composition multiplier is greater than the first threshold value, and high concentration alcohol operating parameters if the fuel composition multiplier is greater than a second threshold value for a number of comparison checks. After a predetermined period, the fuel composition multiplier is updated and re-compared to the first and second thresholds and the appropriate one of the aforementioned operating parameters is implemented.

Abstract: The present invention provides a method for determining ethanol thresholds for a flexible fuel control system for a motor vehicle capable of operating on more than one type of fuel. Preferably, the ethanol threshold is determined from an off-idle purge-free cell from a matrix of fuel adaptive memory cells normally used to compensate for car-to-car variations in required fueling. The ethanol threshold is periodically reduced to compensate for levels of alcohol creep indicated by the amount of purge-free adaptive memory elevation. If the learned value of percent alcohol content of the fuel is less than the ethanol threshold, gasoline operating parameters are implemented for the internal combustion engine. The off-idle purge-free cell also provides a basis for interpolating an on-board diagnostic (OBDII) ethanol threshold. As such, the OBDII monitors are only enabled if the learned value of percent alcohol content of the fuel is less than the OBDII ethanol threshold.

Abstract: A method of controlling a vapor storage canister for a purge control system of an internal combustion engine is provided. The method includes the steps of determining if predetermined conditions are right for controlling a vapor storage canister and maintaining normal fuel feedback operation if the predetermined conditions are not right for controlling the vapor storage canister. The method also includes the steps of determining if the vapor storage canister is loaded if the predetermined conditions are right for controlling the vapor storage canister, maintaining normal fuel feedback operation if the vapor storage canister is not loaded and modifying a duty cycle of a purge solenoid to maximize purge if the vapor storage canister is loaded. The method further includes the steps of updating a loaded canister total purge multiplier and using the total purge multiplier to vary the amount of fuel being delivered to the internal combustion engine.

Abstract: A method of feedback control for an electronic fuel injection system in an internal combustion engine includes the steps of calculating a front O.sub.2 sensor switching voltage threshold based on a signal from a front O.sub.2 sensor upstream of a catalyst in an exhaust system for the engine and from a rear O.sub.2 sensor downstream of the catalyst, comparing a voltage output of the front O.sub.2 sensor to the calculated front O.sub.2 sensor switching voltage threshold to determine if a fuel/air ratio of the engine is rich or lean, and decreasing or increasing an amount of fuel to the engine by fuel injectors of the electronic fuel injection system if the fuel/air ratio is determined rich or lean, respectively.

Abstract: Many internal combustion engines have an auxiliary means for controlling airflow into the engine at idle, such as an Automatic Idle Speed (AIS) motor to compensate for changing load requirements. A method is disclosed for controlling the AIS motor and in turn engine idle speed to compensate for changing loads due to the operation of the air conditioner. The method recognizes the relationship between ambient temperature and pressures generated within the air conditioning compressor and the compensation necessary to maintain a smooth idle speed. The method also utilizes adaptive learning to relate a "looked up" of the air conditioner to the current value of auxiliary air flow required by a warmed up engine.

Abstract: The present invention is a method of firing fuel injectors for an engine of an automotive vehicle. The method includes the steps of determining whether injection timing for firing fuel injectors has changed from one predetermined state to another predetermined state of a distributor reference signal, firing the injectors for a predetermined time period and delivering a calculated amount of fuel for the one predetermined state if the injection timing has not changed. The method also includes determining whether a need for transition fuel has ended if the injection timing has changed and firing the fuel injectors for another predetermined time period and delivering a calculated amount of transition fuel at another predetermined state if the need for transition fuel has not ended.