Air Injection: Description and Operation

AIR System:

SYSTEM DESCRIPTION

NOTE: Always refer to the Underhood Emissions Label first as certain models are NOT equipped with an AIR system.

This system is used to reduce Carbon Monoxide (CO) and Hydrocarbon emissions. This system under certain conditions, adds air to the exhaust manifold to continue combustion after the exhaust gas leaves the combustion chamber. It also heats up the catalytic converter quickly on engine start-up so conversion of exhaust gases will start quickly.

The A.I.R. system includes:

^ An Air Pump:
A belt driven pump on the front of the engine and supplies the air to the system. Intake air passes through a centrifugal filter fan at the front of the pump, where foreign materials are separated from the air by centrifugal force.
^ A Control Valve:
Air flows from the pump through an ECM controlled valve (called a EAC valve) through check valves to either the exhaust ports or the converter.
^ Check Valves:
The check valves prevent back flow of exhaust into the pump in the event of an exhaust backfire or pump drive belt failure.
^ Necessary plumbing.

EAC Valve:

CONTROL VALVE DESCRIPTION

A belt driven AIR pump supplies air through a centrifugal filter fan to the secondary AIR injection bypass valve. The shape of the centrifugal filter fan blades and the direction of fan rotation prevents foreign material from entering the pump with the incoming air.

The AIR bypass valve directs the air to either the engine exhaust manifold ports or to the air cleaner.

The air cleaner acts as a silencer for diverted air. The check valve, on the AIR injection pipe, prevents back flow of the exhaust gases into the AIR pump.

When the engine is started with a coolant temperature above approximately 15°C (45°F), the ECM/PCM energizes the solenoid on the AIR control valve which directs air to the exhaust manifold ports.

1. At higher engine speeds, air can be redirected to the air cleaner by the pressure relief valve even though the solenoid is energized.
2. Air can also be directed to the air cleaner because of any of the following:
^ Low manifold pressure (overrun).
^ Quick vacuum rise (rapid decel).
^ Rich engine condition.
3. The solenoid can be de-energized and air is directed to the air cleaner, under the following conditions:
^ If the engine coolant temperature is too low.
^ If the throttle is opened to power enrichment for more than a short time.
^ If the system is in "CLOSED LOOP" mode.
^ If the MIL (Service Engine Soon) is "ON".
4. Some applications will switch air to the ports for a short time when entering power enrichment. Also, note:
^ Some applications have a "CLOSED LOOP" idle with air directed to the air cleaner.
^ Some applications idle with air directed to the exhaust ports.