Idling control for an otto engine

An idling control for an Otto engine comprises a throttle valve positioned in a suction pipe of an engine intake manifold; a pneumatic cylinder unit operably engaged with said throttle valve by means of a positioning leg; a three-way flow control valve in fluid communication with said pneumatic cylinder unit, said valve having respective input conduits for atmospheric pressure and vacuum, and having means for alternatively transmitting said atmospheric pressure and said vacuum to said pneumatic cylinder unit, said transmitting means including opposing coils and a pulse generator having an adjustable pulse duty factor, said coils being connected to push-pull outputs of said pulse generator, the alternative positions of said control valve being determined in accordance with said duty factor, said duty factor being applied to said opposing coils simultaneously; said three-way flow control valve further includes valve seats for said input conduits and a membrane-like, freely-movable ferromagnetic valve plate having non-magnetic surface layers cooperable with said valve seats; and means for adjusting said pulse duty factor in accordance with engine operating parameters.