Abstract: The knock sensing equipment has a control circuit which generates gating signals for dividing the operation into a measuring phase and a test phase. In the latter, the possible malfunction of the sensor is determined. During the test phase, the sensor responds either to background noise or to a test voltage and the sensing output signals are compared to a predetermined minimum and/or maximum level. Malfunction is indicated if the signals furnished by the sensor are outside of the indicated range.

Abstract: A method and device for adjusting the timing of an internal combustion engine in response to knocking are provided. In the method, knocking signals are generated when the engine knocks and the timing is too far advanced. First correctional signals are generated in response to the knocking signals and adjust at one speed range one of several control curves. Second correctional signals are generated from the first correctional signals to adjust the control curves at the remaining speed ranges. The timing of the engine is retarded in response to the adjusted control curves until the knocking disappears.

Abstract: Engine idle speed is stabilized by a successive three stage control system which sequentially regulates ignition timing, fuel quantity and air throughput volume.

Abstract: In order to suppress the train of detector oscillations after the disappearance of the engine knock phenomenon, the invention provides a piezoelectric oscillator which is set into vibration by engine knock and includes circuitry for applying signals of opposite polarity to the oscillator at times when no engine knock is expected. Accordingly, the output of the piezoelectric engine knock detector is used only in a relatively narrow time interval during the combustion cycle. In the remaining interval, the circuit switches over to a configuration where the oscillations of the piezoelectric oscillator are damped. The construction of the invention makes it possible to discriminate between different cylinders of a multi-cylinder engine and to assign the knock phenomenon to particular engine cylinders. A number of embodiments is presented.