Air Injection: Description and Operation

The secondary air injection system consists of an air injection pump which blows air into the exhaust manifold via a vacuum-controlled secondary air injection control valve (325) in the hose between the air injection pump and exhaust manifold. This valve obtains its control vacuum from the intake manifold.

The secondary air injection pump relay (324) is supplied with current (+30 circuit) when the control valve (584) relay is grounded via pin 19 of the control module.

The control valve relay is supplied with current (+15 circuit) via fuse 19.

The process is activated for 55 seconds or until the temperature of the coolant attains 40°C (104°F). To compensate for the higher power output from the generator, the control module increases the flow of air through the idle air control valve just before the process is activated.





To get the three way catalytic converter working as soon as possible after a cold start, ambient air is pumped into the exhaust manifold where the oxygen in the air starts a chemical reaction together with CO and HC pollutants, thus generating heat.

This process is activated when the engine has been started if the following conditions are fulfilled:

^ coolant temperature -1 to 40°C (30-104°F).
^ engine speed < 4000 rpm.