Abstract: A method is provided for maintaining the speed of a spark-ignited internal combustion engine operating at a desired idle speed to compensate for engine speed variations caused by torque disturbances, utilizing an actual idle speed and the desired idle speed expressed as an RPM error ratio. A desired operating torque ratio is determined based on the torque available, a torque ratio reserve created by retarding spark from the maximum spark advance value and a torque ratio correction which reflects the torque disturbance. A desired final spark advance value is obtained from the desired operating torque ratio utilizing a nonlinear relationship between spark advance and torque ratio. The spark advance is modified to the desired final spark advance value so as to vary the torque supplied by the engine in order to maintain the desired idle speed.

Abstract: A method of inferring and predicting engine torque uses a function of a speed/load table, air/fuel ratio and spark advance. The effects of the magnitudes of engine spark retard, rich or lean air/fuel ratios and exhaust gas recirculation are accounted for using a series of multipliers. Friction torque is accounted for through a speed/air charge table look-up.

Abstract: The method for determining a fault in an exhaust gas recirculation system includes comparing the measured exhaust gas flow of the EGR system to an expected exhaust gas recirculation flow. If the two are not the same the time period that the expected exhaust gas recirculation flow deviates from the measured exhaust gas recirculation flow by a calibrated EGR flow amount is determined. A fault condition in the EGR system is indicated if the duration of the deviation exceeds a predetermined amount of time.

Abstract: An electronic control system for scheduling gearshifts in an automatic transmission includes storing in electronic memory accessible to a microprocessor, functions relating vehicle speed to throttle position, one function being related to each upshift and downshift. Gearshifts are made by probing computer memory with current values for throttle position and vehicle speed, and determining on the basis of the stored shift schedule whether an upshift or downshift is required. Upshift points are determined also on the basis of an empirically determined function relating throttle position and vehicle acceleration immediately before an upshift. Shift control logic commands an upshift on the basis of a predetermined shift schedule, provided minimum vehicle acceleration-engine throttle position criteria are satisfied.

Abstract: A mass airflow based control system for an internal combustion engine is provided which is capable of inferring barometric pressure surrounding the engine. The control system determines the air charge going into the engine from a measured value of mass airflow, and compares this value with a predicted value of air charge going into the engine, which the control system infers. Differences between the two values are first attributed to inlet air temperature, which is measured, and then to a change in barometric pressure, which is the inferred barometric pressure.

Abstract: A mass airflow based control system is provided for an internal combustion engine including a throttle body and an air bypass valve. The system comprises a processor for determining a first value equal to predicted air charge inducted into the engine through the throttle valve, and includes memory for storing an initial value of a ratio of predicted current air charge inducted into the engine to predicted peak air charge capable of being inducted into the engine. The processor determines a second value equal to predicted air charge inducted into the engine through the air bypass valve based on the initial value, and determines a third value equal to predicted peak air charge capable of being inducted into the engine. The processor further determines an actual value of the ratio of predicted current air charge inducted into the engine to predicted peak air charge capable of being inducted into the engine based on the first, second and third values.