Air/Fuel Ratio Control System: Description
The air-fuel ratio feedback control system is designed to control the air-fuel ratio. The air-fuel solenoid valve opens or closes the compensating air bleed and main jet to compensate for rich or lean air-fuel ratio, depending on varying conditions, such as acceleration, deceleration, low coolant temperature, low voltage, etc. These varying conditions are detected by various sensors which transmit corresponding signals to provide air-fuel ratio compensation.
The system uses the exhaust gas sensor located in the exhaust manifold to give an indication of whether the air-fuel ratio is richer or leaner than the stoichiometric point. The stoichiometric point occurs when a chemical reaction is in balance. This balance is given a certain value, and the Electronic Control Unit compares this value to the incoming information in order to compensate and adjust the air-fuel ratio as needed.
The control unit also collects information from the ignition coil negative terminal, water temperature sensor, throttle valve switch, vacuum switch, and altitude switch (on high altitude model).
For improved driveability, the air-fuel ratio solenoid is controlled by open-loop control when the engine is cold, when driving at high speeds or under heavy load, and when the fuel shut-off system is in operation.