| 摘要 |
A method and system for controlling the air-fuel ratio for a carburetor for an internal combustion engine having an intake passage, an exhaust passage, a throttle valve, a detector for detecting the concentration of a constituent of the exhaust gases, an on-off type electromagnetic valve for correcting the air-fuel ratio of the air-fuel mixture supplied by an air-fuel mixture supplier and an electronic controller. The electronic controller comprises a comparing circuit for comparing the output signal of the detector with a stoichiometric reference signal, for driving the on-off electromagnetic valve for controlling the air-fuel ratio to a value approximating the stoichiometric air-fuel ratio. A switch connects a constant signal generating circuit to the electronic controller and renders the electronic control means non-responsive to the detector when a vacuum sensor actuates the switch during a rapid deceleration, whereby the on-off electromagnetic valve operates by the constant signal from the constant signal generating circuit at a predetermined duty ratio to prevent an excessive enrichment of the mixture caused by misfiring.
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