Air Injection: Description and Operation

AIR System (2.8 Liter V6):

SYSTEM OPERATION

The AIR system is used to reduce carbon monoxide and hydrocarbon emissions. The system, under certain conditions, adds air to the exhaust manifold. When this air meets the hot exhaust gases inside the manifold, combustion continues, further oxidizing the HC and CO in the exhaust. These pollutants are then converted into carbon dioxide and water vapor. The additional heat energy released helps to bring the catalyst up to operating temperature more quickly.

The AIR system consists of an air pump, ECM controlled electric air switching valve, ECM controlled vacuum switching valve, check valve, air injector manifold, and connecting hoses.

Pump And filter Fan:

AIR PUMP

The AIR pump is a belt driven positive displacement vane type pump which is permanently lubricated and requires no periodic maintenance. The pump supplies filtered air from a centrifugal filter fan to the electric air control valve where the air is diverted either to the exhaust or to the air cleaner.

Electric AIR Control Valve:

AIR CONTROL VALVE (ELECTRIC)

The air control valve works to direct the air from the air pump to the exhaust system or divert it to the air cleaner, as needed. The valve is operated both electrically (ECM controlled), and by vacuum signal from the intake manifold. When the engine is cold or when the throttle is wide open, the ECM energizes the solenoid on the valve, and air is directed to the exhaust. When the coolant temperature increases, the solenoid is de-energized, and air goes to the air cleaner which also acts as a silencer. At high engine speeds, air is directed to the air cleaner through the pressure relief valve, even if the solenoid is energized. There should be no air pumped into the exhaust while the ECM is in closed loop operation. If air is constantly supplied to the exhaust during closed loop operation the computer senses a false "lean indication". The ECM then responds with a "rich command", and excess fuel is burned in the exhaust system, causing overheating of the catalytic converter, poor fuel economy, and possibly poor driveability. During engine deceleration, or whenever manifold vacuum is high, air is diverted to the air cleaner. If the engine is operating under a constant rich condition, or if the check engine light is on (trouble code is stored), the solenoid is de-energized and air is diverted to the air cleaner.

AIR Manifold:

AIR INJECTOR MANIFOLD

The air injector manifold distributes the pump air to the individual exhaust ports in the cylinder head.

Check Valve:

CHECK VALVE

The check valve is a one-way diaphragm valve which prevents exhaust gas from escaping into the AIR system when the system is not operating, or in the event of a pump or system failure.