Air Injection: Description and Operation

Fig. 83 Air Injection And EGR System Diagram:

PURPOSE
The Air Injection System pumps air through a maintenance-free dry air filter mounted on the pump into the exhaust ports of the cylinder heads to promote oxidation of CO and HC. The heat created by the oxidation process also brings the catalytic converter up to operating temperature more quickly.

OPERATION
Air Injection takes place for about 2 minutes after start up and only when the coolant temperature is between 10°C (50°F) and 40°C (105°F), the engine speed is less than 2500 RPM, the full load contact is open, and the oxygen sensor is in open-loop. Under these conditions the electromagnetic clutch of the air pump is switched on by the CIS - E control unit via the engine systems (MAS) control unit. The engine systems (MAS) control unit simultaneously powers the change-over valve which provides vacuum to the air shut-off valve in the pump circuit. Air is then pumped through the check valves and into the exhaust ports of the cylinder heads.