Air Injection: Description and Operation

PURPOSE
The Pulsed Secondary Air Injection (PAIR) system is used to direct air into the exhaust manifold to extend the combustion of unburned hydrocarbons (HC) and carbon monoxide (CO) in the exhaust system. This air is also used as the oxygen source for the catalytic converter.

OPERATION
During normal driving conditions with low coolant temperatures the PAIR control valve is held open by the Vacuum Switching Valve (VSV). The VSV is activated by the Engine Control Module (ECM) with input from various sensors. Vacuum created by exhaust pulses opens the reed valve and air is drawn into the exhaust stream. This action also occurs on deceleration at normal operating coolant temperatures when the throttle plate is closed at certain RPM's.