Air Flow System
Air is drawn in through air cleaner and is measured by the air flow meter. Air then travels through throttle chamber and into intake manifold. A throttle valve in the chamber controls air flow while driving. At idle, throttle valve is almost closed and air is drawn through a by-pass port in throttle chamber. Idle speed adjusting screw controls quantity of air intake at idle. During warm-up operation, extra air is by-passed through air regulator to increase engine RPM.
The oxygen sensor detects the amount of oxygen in the exhaust gases. If the sensor senses too much or too little oxygen in the exhaust gases, a change in voltage is produced in the sensor and is transmitted to the ECU. The ECU then changes the amount of fuel injected by using the modulating valve to vary the length of time injectors are on. This varying injection time leans or richens the air/fuel ratio, keeping the air/fuel ratio very close to the stoichiometric value of 14.5 to 1.