Air Injection: Operation

The air pump operates whenever the engine is running. A pressure relief valve diverts air to atmosphere whenever pump pressure exceeds 6.5 psi (.43 kg/cm² ). When engine coolant is below 130°F (55°C), air passes through the thermostatic air slide valve and is directed to the exhaust manifold. As the engine warms up, less air is directed to the exhaust manifold and some is sent to the catalytic converter. When coolant is above 131 °F (55°C), all injected air through the thermostatic slide valve is sent to the catalytic converter.

When manifold vacuum is high, the vacuum switch opens the electrovalve. This allows a small amount of air to the exhaust manifold. The oxygen sensor interprets this as a lean mixture and the electronic control unit richens the mixture slightly. The result is better driveability at small throttle openings. When the throttle is wide open for more than about 15 seconds, air injection is stopped because vacuum signal is not strong enough to open the diverter valve. The delay valve keeps the diverter valve open (to continue injection) if the throttle is wide open for brief periods of less than 11-17 seconds.