Abstract: An engine includes a plurality of combustion cylinders configured to burn a fuel to power the engine, and a plurality of fuel injectors. Each of the fuel injectors is arranged to distribute fuel delivered from a fuel tank to one of the plurality of combustion cylinders. The engine also includes a controller programmed to adjust a fuel trim signal gain based on sensing exhaust flow downstream of the combustion cylinders. The controller is also programmed to monitor a cumulative misfire count for each of the plurality of combustion cylinders. The controller is further programmed to issue a prognosis message identifying a state of health of at least one of the plurality of fuel injectors in response to a fuel trim signal gain exceeding an adjustment threshold and a cumulative misfire count greater than a misfire threshold.

Abstract: An engine includes a plurality of combustion cylinders configured to burn a fuel to power the engine, and a plurality of fuel injectors. Each of the fuel injectors is arranged to distribute fuel delivered from a fuel tank to one of the plurality of combustion cylinders. The engine also includes a controller programmed to adjust a fuel trim signal gain based on sensing exhaust flow downstream of the combustion cylinders. The controller is also programmed to monitor a cumulative misfire count for each of the plurality of combustion cylinders. The controller is further programmed to issue a prognosis message identifying a state of health of at least one of the plurality of fuel injectors in response to a fuel trim signal gain exceeding an adjustment threshold and a cumulative misfire count greater than a misfire threshold.

Abstract: A fuel control system for an engine includes a closing module and a purge control module. The closing module commands closing of a purge valve in response an engine speed transitioning from greater than a predetermined speed to less than the predetermined speed while the purge valve is in an open state. The predetermined speed is less than a predetermined target speed of the engine and is greater than zero. The purge control module transitions the purge valve from the open state to a closed state in response to the command.

Abstract: A fuel control system for an engine includes a closing module and a purge control module. The closing module commands closing of a purge valve in response an engine speed transitioning from greater than a predetermined speed to less than the predetermined speed while the purge valve is in an open state. The predetermined speed is less than a predetermined target speed of the engine and is greater than zero. The purge control module transitions the purge valve from the open state to a closed state in response to the command.

Abstract: A diagnostic system for a vehicle is disclosed. A first difference module generates a first difference based on a first pressure measured at a first secondary air injection (SAI) valve and a previous value of the first pressure. A first summer module generates a first accumulated difference based on a sum of values of the first difference generated during a predetermined period. A second difference module generates a second difference based on a second pressure measured at a second SAI valve and a previous value of the second pressure. A second summer module generates a second accumulated difference based on a sum of values of the second difference generated during the predetermined period. A fault indication module selectively indicates that a fault is present downstream of one of the first and second SAI valves based on the first and second accumulated differences.

Abstract: A fault diagnostic system of a vehicle includes an error module, a proportional integral (PI) module, and a fault module. The error module determines an error based on a difference between a sample of a signal generated by an exhaust gas oxygen sensor and a target value of the sample. The PI module determines a proportional correction based on the error, determines an integral correction based on the error, and determines a fueling correction based on the proportional and integral corrections. The fault module selectively diagnoses a fault based on the integral correction and the fueling correction.

Abstract: Fueling to one cylinder of an engine is selectively adjusted based on a correction associated with the cylinder. An instability module increments a counter value when the correction is equal to one of a first predetermined value and a second predetermined value and was previously equal to the other one of the first and second predetermined values. The instability module selectively generates a first indicator based on the counter value. A variance of imbalance values can be determined based on samples of an exhaust gas oxygen signal. Two variances are determined: one variance with adjustment based on the correction, one without adjustment based on the correction. A variance checking module selectively generates a second indicator based on the first and second variances. A re-synchronization module re-synchronizes the imbalance values with the cylinders, respectively, in response to generation of the first indicator and/or the second indicator.

Abstract: A fault diagnostic system of a vehicle includes an error module, a proportional integral (PI) module, and a fault module. The error module determines an error based on a difference between a sample of a signal generated by an exhaust gas oxygen sensor and a target value of the sample. The PI module determines a proportional correction based on the error, determines an integral correction based on the error, and determines a fueling correction based on the proportional and integral corrections. The fault module selectively diagnoses a fault based on the integral correction and the fueling correction.

Abstract: A system for a vehicle includes a change determination module, a sulfur determination module, and a final equivalence ratio (EQR) module. The change determination module estimates a change in an amount of sulfur within a catalyst of an exhaust system of the vehicle. The sulfur determination module estimates the amount of sulfur within the catalyst based on the change. The final EQR module selectively adjusts fueling of an engine based on the amount of sulfur.

Abstract: A diagnostic system for a vehicle is disclosed. A first difference module generates a first difference based on a first pressure measured at a first secondary air injection (SAI) valve and a previous value of the first pressure. A first summer module generates a first accumulated difference based on a sum of values of the first difference generated during a predetermined period. A second difference module generates a second difference based on a second pressure measured at a second SAI valve and a previous value of the second pressure. A second summer module generates a second accumulated difference based on a sum of values of the second difference generated during the predetermined period. A fault indication module selectively indicates that a fault is present downstream of one of the first and second SAI valves based on the first and second accumulated differences.

Abstract: An air/fuel imbalance (AFIM) diagnostic system comprises a first module, an imbalance determination module, and an imbalance diagnostic module. The first module outputs imbalance data samples based on an oxygen signal provided by an oxygen sensor measuring oxygen in exhaust expelled from cylinders of a cylinder bank. The imbalance determination module determines an AFIM value based on the imbalance data samples. The imbalance diagnostic module selectively diagnoses an AFIM in the cylinder bank based on the AFIM value.

Abstract: A system for a vehicle includes a change determination module, a sulfur determination module, and a final equivalence ratio (EQR) module. The change determination module estimates a change in an amount of sulfur within a catalyst of an exhaust system of the vehicle. The sulfur determination module estimates the amount of sulfur within the catalyst based on the change. The final EQR module selectively adjusts fueling of an engine based on the amount of sulfur.

Abstract: Fueling to one cylinder of an engine is selectively adjusted based on a correction associated with the cylinder. An instability module increments a counter value when the correction is equal to one of a first predetermined value and a second predetermined value and was previously equal to the other one of the first and second predetermined values. The instability module selectively generates a first indicator based on the counter value. A variance of imbalance values can be determined based on samples of an exhaust gas oxygen signal. Two variances are determined: one variance with adjustment based on the correction, one without adjustment based on the correction. A variance checking module selectively generates a second indicator based on the first and second variances. A re-synchronization module re-synchronizes the imbalance values with the cylinders, respectively, in response to generation of the first indicator and/or the second indicator.

Abstract: A control system comprising an oxygen sensor that generates an oxygen signal based on an oxygen concentration level in an exhaust gas of an engine, a filtering module that determines a filtered signal based on the oxygen signal, and an air-fuel imbalance detection module that detects an air-fuel imbalance in the engine based on the oxygen signal and the filtered signal. A method comprising generating an oxygen signal based on an oxygen concentration level in an exhaust gas of an engine, determining a filtered signal based on the oxygen signal, and detecting an air-fuel imbalance in the engine based on the oxygen signal and the filtered signal.

Abstract: An air/fuel imbalance (AFIM) diagnostic system comprises a first module, an imbalance determination module, and an imbalance diagnostic module. The first module outputs imbalance data samples based on an oxygen signal provided by an oxygen sensor measuring oxygen in exhaust expelled from cylinders of a cylinder bank. The imbalance determination module determines an AFIM value based on the imbalance data samples. The imbalance diagnostic module selectively diagnoses an AFIM in the cylinder bank based on the AFIM value.

Abstract: A control system comprising an oxygen sensor that generates an oxygen signal based on an oxygen concentration level in an exhaust gas of an engine, a filtering module that determines a filtered signal based on the oxygen signal, and an air-fuel imbalance detection module that detects an air-fuel imbalance in the engine based on the oxygen signal and the filtered signal. A method comprising generating an oxygen signal based on an oxygen concentration level in an exhaust gas of an engine, determining a filtered signal based on the oxygen signal, and detecting an air-fuel imbalance in the engine based on the oxygen signal and the filtered signal.