Abstract: A system and method for flexible fuel ethanol concentration and hardware malfunction detection compares a current hardware reference value learned based on an air-fuel ratio detected during a pre-fuel mix period with a previous hardware reference value from a previous vehicle driving cycle, and detects a hardware malfunction when a difference between current and previous hardware reference values exceeds a predetermined threshold. The system and method also monitors the air-fuel ratio during a post-fuel mix period, and detects a hardware malfunction when the air-fuel ratio changes by more than a predetermined threshold during the post-fuel mix period. The system and method also compares an observed slope of the air-fuel ratio detected during a fuel mixing period over an amount of fuel consumed with an expected slope when a cold-start is detected, and detects a hardware malfunction when a difference between observed and expected slopes exceeds a predetermined threshold.

Abstract: A system and method for flexible fuel ethanol concentration and hardware malfunction detection compares a current hardware reference value learned based on an air-fuel ratio detected during a pre-fuel mix period with a previous hardware reference value from a previous vehicle driving cycle, and detects a hardware malfunction when a difference between current and previous hardware reference values exceeds a predetermined threshold. The system and method also monitors the air-fuel ratio during a post-fuel mix period, and detects a hardware malfunction when the air-fuel ratio changes by more than a predetermined threshold during the post-fuel mix period. The system and method also compares an observed slope of the air-fuel ratio detected during a fuel mixing period over an amount of fuel consumed with an expected slope when a cold-start is detected, and detects a hardware malfunction when a difference between observed and expected slopes exceeds a predetermined threshold.

Abstract: A method of controlling an engine during starting is disclosed. During cold starting and following a refueling, a default alcohol value is used to control various systems associated with the engine, including fuel injection and ignition timing. The default alcohol value is used to ensure reliable starting. During non-cold starting and following a refueling, the current alcohol value is used to minimize fuel inefficiencies.