1. In an internal combustion engine having a signalling device for signalling an acceleration demand and a deceleration demand, and a fuel control system of the type having speed pulse generating means responsive to engine speed operative to generate a pulse train of fixed duration speed pulses having a pulse repetition rate varying directly with engine speed and an interpulse interval varying inversely with engine speed, computing means operative to generate an output signal indicative of engine fuel requirement, and injector valve means actuable in response to the computing means output signal to control the fuel delivered to the signal, an improved deceleration fuel control circuit comprising: a. an output switch having an output switch control electrode and an output switch output electrode connected to said computing means, said output switch operative to provide at said output switch output electrode a normal fuel output level and a fuel cutoff output level, said normal fuel output level operative to permit said computing means to normally generate said output signals and said fuel cutoff signal operative to cause said computing means to generate output signals reducing the fuel delivered to the engine; b. a first control switch operative to control said output switch having a first control switch output electrode connected to said output switch control electrode and a first control switch control electrode connected to said signalling device, said first control switch operative to normally provide at said first control switch output electrode a first control switch first output level when said signalling device signals said deceleration demand and a first control switch second output level when said signalling device signals said acceleration demand; c. a second control switch for controlling said first control switch having a second control switch control electrode connected to said speed pulse generating means and a second control switch output electrode connected to said first control switch control electrode, said second control switch being responsive to voltages at said second control switch control electrode to permit said first control switch to normally provide said first control switch second output level for second control switch control electrode voltages below a first predetermined speed dependent level when said signalling means signals said deceleration demand so as to permit said output switch to provide said normal fuel output level and to otherwise control said first control switch to provide said first control switch first output level for control switch control electrode voltages above said predetermined speed dependent level so as to control said output switch to provide said fuel cutoff output level; d. a multiple-pulse interval-averaging capacitor connected to said second control switch control electrode operative to provide a second control switch control electrode voltage indicative of an average of a plurality of said engine speed pulse intervals, said second control switch control electrode voltages varying with said repetition rate of said speed pulses so as to control said second control switch to control said first control switch to provide said second output level For causing said output switch to provide said fuel cutoff output level whenever said voltage provided by said multiple-pulse interval-averaging capacitor exceeds said first predetermined engine speed dependent voltage; and e. inter-pulse interval computing means connecting said pulse generating means and said first control switch control electrode for controlling said first control switch to provide said first output level so that said output switch provides said normal fuel output level whenever an interval between two successive pulses is indicative of an engine speed less than a second predetermined engine speed dependent level less than said first predetermined engine speed dependent level, said inter-pulse computing means comprising a source of constant potential, a resistor and a computing capacitor connected in series to said source of constant potential, a first discharge switch, a second discharge switch, and voltage divider means, said first discharge switch having a first discharge switch control electrode connected to said pulse generating means and a first discharge switch discharge electrode connected intermediate said resistor and said computing capacitor operative to discharge said computing capacitor during each said fixed duration of said fixed duration speed pulses, said second discharge switch having an output electrode connected to said first control switch control electrode, second discharge switch discharge electrode connected intermediate said resistor and said computing capacitor, and a second discharge switch control electrode, said voltage divider means connected intermediate said source of constant potential and said second discharge switch control electrode operative to provide thereat a second discharge switch control electrode voltage indicative of said second predetermined engine speed dependent level, whereby said computing capacitor is discharged through said second discharge switch to control said first control switch to provide said second output level whenever the interval between successive speed pulses allows said computing capacitor to charge from said constant potential source to a level above said second predetermined engine speed dependent level before being discharged by said first discharge switch.

2. In an internal combustion engine having a first signalling device for signalling an acceleration demand and a deceleration demand, a second signalling device for signalling engine operation modes including a Park mode and a Neutral mode, and a fuel control system of the type having speed pulse generating means responsive to engine speed operative to generate a pulse train of fixed duration speed pulses having a pulse repetition rate varying directly with engine speed and an inter-pulse interval varying inversely with engine speed, computing means operative to generate an output signal indicative of engine fuel requirement, and injector valve means actuable in response to the computing means output signal to control the fuel delivered to the signal, an improved deceleration fuel control circuit comprising: a. an output switch having an output switch control electrode connected to said second signalling device and an output switch output electrode connected to said computing means, said output switch operative to provide at said output switch output electrode a normal fuel output level and a fuel cutoff output level, said normal fuel output level being provided when said second signalling device signals one of said Park and Neutral modes to normally permit said computing means to normally generate said output signals and said fuel cutoff signal operative to cause said computing means to generate output signals reducing the fuel delivered to the engine; b. a first control switch operative to control said output switch having a first control switch output electrode connected to said output switch control electrode and a first control switch electrode connected to said first signalling device, said first control switch operative to normally provide at said first control switch output electrode a first control switch first output level when said first signalling device signals said deceleration demand and a first control switch second output level when said first signalling device signals said acceleration demand; c. a second control switch for controlling said first control switch having a second control switch control electrode connected to said speed pulse generating means and a second control switch output electrode connected to said first control switch control electrode, said second control switch being responsive to voltages at said second control switch control electrode to permit said first control switch to normally provide said first control switch second output for second control switch control electrode voltages below a first predetermined speed dependent level when said first signalling means signals said deceleration demand so as to permit said output switch to provide said normal fuel output level and to otherwise control said first control switch to provide said first control switch first output level for the control switch control electrode voltages above said predetermined speed dependent level so as to control said output switch to provide said fuel cutoff output level; d. a multiple-pulse interval-averaging capacitor connected to said second control switch control electrode operative to provide a second control switch control electrode voltage indicative of an average of a plurality of said engine speed pulse intervals, said second control switch control electrode voltages varying with said repetition rate of said speed pulses so as to control said second control switch to control said first control switch to provide said second output level for causing said output switch to provide said fuel cutoff output level whenever voltage provided by said multiple-pulse interval-averaging capacitor exceeds said first predetermined engine speed dependent voltage; and e. single inter-pulse interval computing means connecting said pulse generating means and said first control switch control electrode for controlling said first control switch to provide said first output level so that said output switch provides said normal fuel output level whenever the interval between two successive speed pulses is indicative of an engine speed less than a second predetermined engine speed dependent level less than said first predetermined engine speed dependent level, said inter-pulse computing means comprising a source of constant potential, a resistor and a computing capacitor connected in series to said source of constant potential, a first discharge switch, a second discharge switch, and voltage divider means, said first discharge switch having a first discharge switch control electrode connected to said pulse generating means and a first discharge switch discharge electrode connected intermediate said resistor and said computing capacitor operative to discharge said computing capacitor during each said fixed duration of said fixed duration speed pulses, said second discharge switch having an output electrode connected to said first control switch control electrode, second discharge switch discharge electrode connected intermediate said resistor and said computing capacitor, and a second discharge switch control electrode, said voltage divider means connected intermediate said source of constant potential and said second discharge switch control electrode operative to provide thereat a second discharge switch control electrode voltage indicative of said second predetermined engine speed dependent level, whereby said computing capacitor is discharged through said second discharge switch to control said first control switch to provide said second output level whenever the interval between successive speed pulses allows said computing capacitor to charge from said constant potential source to a level above said second predetermined engine speed dependent level before being discharged by said first discharge switch.