Abstract: LPG decompressed in a regulator is fed as primary fuel into an intake passage from a carburetor, and is fed as supplementary fuel to the intake passage from an injector. An ECU controls a control variable for the injector to cause an air/fuel ratio detected in an oxygen sensor to be a stoichiometric air/fuel ratio. At idle operation, an optimum state of the control variable with respect to a target value is output from a monitor terminal and is monitored, and an adjusting screw in a slow passage is operated and adjusted to cause the control variable to be the target value. An adjustment range for the control variable is set into two stages through operation of the test terminal. The ECU controls an output pattern of a monitor terminal in individual adjustment ranges at each stage, according to whether or not the control variable falls within the adjustment range.

Abstract: LPG decompressed in a regulator 3 is fed as primary fuel into an intake passage 6 from a carburetor 9, and is fed as supplementary fuel to the intake passage 6 from an injector 11. An ECU 4 controls a control variable for the injector 11 to cause an air/fuel ratio detected in an oxygen sensor 53 to be a stoichiometric air/fuel ratio. In an idle operation, an optimum state of the control variable with respect to a target value is output from a monitor terminal 57 and is monitored, and an adjusting screw 37 in a slow passage 36 is operated and adjusted to cause the control variable to be the target value. An adjustment range for the control variable is set into two stages through operation of the test terminal 56. The ECU 4 controls an output pattern of a monitor terminal 57 in individual adjustment ranges at each stage, according to whether or not the control variable falls within the adjustment range.

Abstract: An electronic air-fuel mixture control system is adapted to an internal combustion engine to determine an optimum air-fuel ratio in dependence upon renewal of a plurality of learning values related to a plurality of load regions of the engine. The control system is arranged to conduct simultaneous learning of the learning values at a frequency in accordance with lapse of time and to conduct selective learning of the learning values in accordance with change of the load acting on the engine.

Abstract: An electronic air-fuel mixture control system is adapted to an internal combustion engine to determine an optimum air-fuel ratio in dependence upon renewal of plural learning values related to a plurality of load regions of the engine. The control system is arranged to select one of the learning values in accordance with the engine load and to prohibit learning of the selected learning value when a difference between the selected learning value and the adjacent learning value is more than an allowable value determined in consideration with allowable fluctuation of the air-fuel ratio caused by change of the amount of air flowing into the engine.

Abstract: In a carburetor having a flow control element axially movable within an air bleed passage in the carburetor body for controlling the cross-sectional area of the passage and a stepper motor on the body for effecting axial movement of the control element, an input circuit produces an electric signal indicative of the operating condition of an engine. A computer determines rotary steps of the motor in response to the electric signal for optimizing the cross-sectional area of the passage in relation to the operating condition of the engine, an a whether the number of the determined rotary steps is more than the actual rotary steps of the motor. A first command signal and a second command signal, and first and second control signals are produced respectively for effecting one rotary step of the motor in a direction defined by each of the command signals.