Abstract: A failsafe engine fuel control system is disclosed in which a primary control signal, normally a direct function of an engine manifold pressure sensor signal, is utilized by an electronic engine control microprocessor to calculate control signals for engine fuel injectors and engine spark apparatus. Pressure sensor failure detection apparatus is provided which, in the event of the engine manifold pressure sensor signal being non-representive of actual engine manifold pressure, results in making the primary control signal utilized by the microprocessor a direct function of at least an analog sensor signal representative of engine throttle position rather than engine manifold pressure. Preferably, in the event of a pressure sensor failure the primary control signal is calculated as a function of both a throttle position signal and an engine speed signal.

Abstract: An acceleration fuel enrichment system is disclosed in which if the rate of increase of throttle position is determined as exceeding a predetermined minimum threshold (V.sub.1), asynchronous acceleration enrichment fuel control pulses are developed and effectively added to steady state synchronous base fuel control pulses provided by an engine control microprocessor. When the rate of throttle position increase falls below a preset level, the development of the asynchronous fuel control pulses is terminated and synchronous acceleration enrichment fuel pulses are provided which are effectively added to the base synchronous fuel control pulses. The durations of these synchronous acceleration enrichment pulses are initially fixed, but when a decrease in engine manifold pressure is sensed, these durations are determined in accordance with the rate of change of the magnitude of sensed engine manifold pressure.

Abstract: Any offset error in the throttle position sensor reading of a fuel injection circuit can be corrected by determining the actual reading at a time when the reading should correctly be zero, then adjusting subsequent readings by the error figure. The error calculation is continually updated during periods of nearly-closed throttle, and is maintained between such periods. If the error exceeds a limit value, an "error" signal is provided.

Abstract: During engine cranking and after cranking if engine coolant temperature has not yet exceeded a minimum value, an air bypass valve (dashpot) provides maximum additional air to the engine fuel mixture in addition to the air provided in accordance with engine throttle position. During normal engine run conditions with the throttle not effectively closed, the dashpot provides minimum additional air to the fuel mixture. During deceleration when engine throttle is effectively closed, if engine speed is at least a maximum speed IDLEH and then declines, effective dashpot actuation will be 100% (maximum additional air) for engine speeds at least equal to IDLEH, 0% for engine speeds below a minimum speed IDLEL, and for engine speeds between IDLEH and IDLEL, the change (decrease) in dashpot actuation will be proportional to the change in current engine speed and substantially independent of time. If during deceleration engine speed decreases to IDLEL, then dashpot actuation remains at a minimum.