Air Injection: Description and Operation

Emission Control System Schematic:

PURPOSE
The air injection reactor system pumps air from a maintenance-free dry air filter mounted on the pump into the exhaust ports of the cylinder head 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 a about 110 seconds after start up and only when the coolant temperature is between 10 °C (50 °F) and 40 °C (104 °F), the engine speed is less than 3600 RPM, a specific intake air mass is not exceeded and the oxygen sensor is in open-loop.

Under these conditions the electromagnetic clutch of the air pump (125) is switched on by the HFM-SFI control module (N3/1). The HFM-SFI control module simultaneously powers the air injection switch-over valve (Y32) which provides vacuum to the air injection shut-off valve (126) in the pump circuit. Air is then pumped through the check valve (127) and into the exhaust ports of the #'s 3 and 4 cylinder in the cylinder head.