Abstract: A method of filtering an oxygen sensor signal is provided. The method includes obtaining the oxygen sensor signal from the oxygen sensor on a periodic basis. The oxygen sensor signal is then compared to an average oxygen sensor signal value. If the oxygen sensor signal is greater than the average oxygen sensor signal value, a high signal counter is incremented. If the high signal counter is greater than a high signal count threshold, the oxygen sensor signal is forced to a high signal value. If the oxygen sensor signal is less than the average oxygen sensor signal value, a low signal counter is incremented. If the low signal counter is greater than a low signal count threshold, the oxygen sensor signal is forced to the low signal value. The high and low signal count thresholds correspond to a preselected period of time indicating a low or high signal trend within the oxygen sensor signal.

Abstract: The present invention provides a flexible fuel compensation system for determining the percent alcohol content of fuel in a flexible fueled vehicle at the instance of fueling and in an open loop operating mode. According to the invention, two estimated percent alcohol content values are calculated based on the old fuel mixture's alcohol content and two fueling possibilities. A first value is calculated for the possibility that E85 fuel was added to the tank and a second value is calculated for the possibility that E0 fuel was added to the tank. If the inferred ethanol content increases above a positive threshold during closed loop operation, the system assumes that E85 fuel has been added to the tank. Conversely, if the inferred ethanol content decreases below a negative threshold, the system assumes that E0 fuel was added to the tank.

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 provides a method of compensating for a boil-off condition in a flexible fuel compensation control system for a flexible fueled vehicle with a PCV solenoid. The methodology determines both the presence and extent of boil-off corruption and handles closed loop controls normally as if no boil-off corruption exists. The methodology also determines the amount of boil-off corruption being introduced through the PCV system and updates the flexible fueled vehicle fueling during a blend change between ethanol and gasoline. Additionally, the methodology determines when boil-off corruption is no longer influencing closed loop fuel control.

Abstract: The present invention provides a method for controlling combustion parameters of an internal combustion engine during wide open throttle or part throttle enrichment operation. Oxygen sensor rich and lean counts above and below a stoichiometric air/fuel ratio are counted during an injector pulse width period while a fuel concentration determination is being made at wide open throttle and part throttle enrichment. The ratio of lean counts to rich counts is compared to a calibratable value for incrementing the fuel concentration delivered to the internal combustion engine. The fuel concentration is further controlled if a boil-off condition is detected.

Abstract: The present invention provides a flexible fuel compensation system for determining the percent alcohol content of fuel in a flexible fueled vehicle at the instance of fueling and in an open loop operating mode. According to the invention, two estimated percent alcohol content values are calculated based on the old fuel mixture's alcohol content and two fueling possibilities. A first value is calculated for the possibility that E85 fuel was added to the tank and a second value is calculated for the possibility that E0 fuel was added to the tank. If the inferred ethanol content increases above a positive threshold during closed loop operation, the system assumes that E85 fuel has been added to the tank. Conversely, if the inferred ethanol content decreases below a negative threshold, the system assumes that E0 fuel was added to the tank.

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 controlling the combustion parameters of an internal combustion engine with an oxygen sensor prior to a closed loop operating condition. If the output voltage of the oxygen sensor indicates a lean air to fuel ratio condition, the percent alcohol content is incremented to a limit based on an E85 possibility curve. If the voltage output of the oxygen sensor indicates a rich air to fuel ratio condition, the percent alcohol content is decremented to a limit based on an E0 possibility curve. After the end of the fuel blending period or when the internal combustion engine reaches a closed loop mode, control of the combustion parameters of the internal combustion engine are returned to normal regime oxygen sensor feedback control.

Abstract: A method of measuring temperature of a catalytic converter in a motor vehicle includes the step of determining a first oxygen sensing mechanism output, determining if it is time to determine a second oxygen sensing mechanism output, and determining the second oxygen sensing mechanism output if it is time to determine the second oxygen sensing mechanism output. The method also includes the step of determining a change in oxygen sensing mechanism output by taking a difference between the first oxygen sensing mechanism output and the second oxygen sensing mechanism output. The method further includes the step of finding a catalytic converter temperature in a look-up table using the change in oxygen sensing mechanism output, and using the catalytic converter temperature as needed by an electronic control mechanism to operate an engine of the motor vehicle.

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 flexible fuel compensation system including a method of methanol boil-off compensation. The methanol boil-off compensation method includes an initialization routine, a run mode routine and a shutdown routine. The method will monitor a plurality of flags to determine when the methanol boil-off compensation should be used.

Abstract: A method is provided for checking the function of a fuel composition sensor and for learning the percent alcohol content of a fuel used in a motor vehicle capable of operating on more than one type of fuel, as an alternative to a fuel composition sensor. The present invention improves the reliability of a motor vehicle utilizing a fuel composition sensor by allowing vehicle operation to continue uninterrupted, such as when a short or open condition exists within the sensor. The method first determines whether conditions are such that the percent alcohol content of a fuel should be "learned". If conditions are appropriated, then necessary engine operating conditions are first initialized. The oxygen sensor output signal is checked to determine whether the engine is operating too rich or lean. The value of percent alcohol content stored in the engine control unit's memory is modified in the direction of stoichiometric engine operation.

Abstract: A flexible fuel vehicle is a vehicle capable of operating on alcohol, gasoline, or any combination of these two fuels. Because of the unique properties of alcohol fuels, modifications to engine operating characteristics are required to compensate for the varying percentage of alcohol in the fuel. A method is provided for determining the percent alcohol content of the fuel in the fuel tank, utilizing the oxygen sensor feedback control loop to sense changes in air/fuel ratio and relay that information to the engine controller so that dependant variables can be adjusted accordingly. The method includes placing the fuel pump in the fuel tank along with a mixed fuel accumulator so that a known and slowly varying percentage of alcohol in the fuel is provided to the engine, especially during open loop operation.

Abstract: A system and method for the detection and correction of purge corruption in the adaptive memory portion of a control system controlling, in part, the fuel to air ratio during the cold start up of an internal combustion engine. This is achieved by performing two calibrations (or updates) of the adaptive memory cells (or locations) during the previous engine operation. The adaptive memory is first updated with the purge system off. The memory locations addressed at this time are denoted as the purge free adaptive memory cells. Next, the adaptive memory is updated with the purge system on. These memory locations are denoted as the normal adaptive memory cells. During the next cold engine start, purge corruption of the adaptive memory is detected when the difference between the two calibrations exceeds a value representing an absence of purge corruption.