General System Description

Fig. 2 Feedback control system.:

The feedback control system, Fig. 2, maintains proper air/fuel mixture ratio by allowing air into the intake manifold, to adjust a temporarily rich fuel condition. This system is made up of two sub-systems: the X-system and the M-system.
The X-system consists of air control valve B, frequency solenoid valve B, consistent vacuum valve on all 1984 models, check valves, surge tanks A and B, and the control unit. When frequency solenoid valve B is opened by the control unit, manifold vacuum is applied to air control valve B. When valve B opens, it allows correct amount of air to be fed into the intake manifold.
The feedback control solenoid valve is provided to stop feedback operation under low engine speed and cold engine temperature.
Surge tank A and check valves act as a vacuum reservoir, while surge tank B dampens the vacuum pulses so that steady vacuum is applied to air control valve B. The M-system consists of air control valve A, frequency solenoid valve A, control unit and a check valve. When frequency solenoid valve A is opened by the control unit, air control valve A, which has already been opened by vacuum from the carburetor port, feeds the correct amount of air into the intake manifold. The amount of air is proportional to intake air volume.