Air Injection: Description and Operation

PURPOSE
The Air Injection system adds air to the already burning exhaust gases during cold running, reducing HC and CO.

Air Injection Diagram:

OPERATION
During a cold start, when the catalytic converter is not at operating temperature, the DME control module grounds the air pump relay, energizing the air pump clutch and the changeover valve for a maximum of 125 sec. if:

^ Start signal present
^ Engine speed below 4,600 rpm
^ Engine temperature below 104°F (40°C) (engine coolant temp. sensor)


The air pump provides injected air to the exhaust system via vacuum controlled valve (11) and check valve (12). If vacuum valve (11) is not opened by the changeover valve air pressure will be vented to the atmosphere.

At normal operating temperature air injection does not occur since the catalytic converter reduces the exhaust emissions well below emission control standards.