Air Injection: Description and Operation

PURPOSE
The air injection system reduces the hydrocarbon (HC) and carbon monoxide (CO) in the exhaust gases by continuing the combustion of unburned gases after they enter the exhaust system. This is done by injecting fresh air in front of the exhaust valves or into the catalytic converter to continue the burning process of hydrocarbon and carbon monoxide.

Fig. 28 Air Flow In Injection System With High Or Low Engine Load (Engine Cold, First 60 Seconds):

OPERATION
Engine temperature below 35 °C (95 °F):
The outside air is drawn through a special air cleaner into the air pump. Each time the engine is started, power is applied (by the acceleration enrichment relay) to the electrical vacuum solenoid valve for 60 seconds. This opens the vacuum line from the throttle valve to switching valve #1. The injection air is now routed from the air pump through switching valve #1 to the check valve. From there it goes through the air tube system, where at the end, it gets injected in front of the exhaust valves.

Fig. 29 Air Flow In Injection System With Low Engine Load (Engine Hot Or After 60 Seconds When Engine Cold):

After 60 seconds the electrical vacuum solenoid valve closes, and the vacuum line to switching valve #1 is blocked. Now the injection air is routed to switching valve #2, which is controlled by vacuum taken from the throttle valve. At idle speed and partial load (high vacuum), the air is routed through switching valve #2 to the check valve. From there it goes through the air tube, where at the end, it gets injected into the catalytic converter.

Fig. 30 Air Flow In Injection System With High Engine Load (Engine Hot Or After 60 Seconds When Engine Cold):

During acceleration and full engine load (low vacuum), the air flows through switching valve #2 and from there it is routed into the air cleaner housing. There it is used as regular intake air.

Engine temperature above 35 °C (95 °F):
At idle speed and partial load (high vacuum), the air comes from the air pump through switching valve #1 and gets routed to switching valve #2. From there it goes through the check valve into the air tube, where at the end, it gets injected into the catalytic converter. During acceleration and full engine load (low vacuum), the air flows from the air pump through switching valve #1 to switching valve #2 and from there it is routed into the air cleaner housing. There it is used as regular intake air.


COMPONENTS:


Air Cleaner
The air cleaner (located at left side of engine in front of air pump) filters the outside air before it enters the air pump. The air filter element should be replaced every 48,000 km (30,000 miles).


Air Pump
The air pump (located on left side, front of engine) produces the air pressure to operate the air injection system. It is driven by the camshaft pulley via a V-belt. The air pump is maintenance free, but the V-belt needs to be checked for aging, wear and tension every 48,000 km (30,000 miles).


Vacuum Solenoid Valve
The solenoid valve is controlled by an electrical signal from the acceleration enrichment relay. It controls the vacuum flow from the throttle housing to switching valve #1. It opens the vacuum connection for 60 seconds after engine start-up when engine temperature is below 35 °C (95 °F). If engine temperature is above 35 °C (95 °F), the solenoid valve remains closed at all times.

Fig. 7 Switching Valve #1 And #2:

Diverter Valve #1
The switching valve #1 (located to the side of left bank valve cover, in front of air pump) is controlled by a vacuum control signal taken from the throttle valve. Inline with the vacuum hose is the solenoid valve which can open or close the vacuum connection. When the vacuum connection is open (first 60 seconds when engine temperature is below 35 °C or 95 °F), the injection air flows through switching valve #1 to the exhaust valves. When the vacuum connection is closed (after 60 seconds or engine temperature is above 35 °C or 95 °F), the injection air flows through switching valve #1 to switching valve #2.


Diverter Valve #2
Switching valve #2 (located above right bank valve cover, in front of power steering pump) is operated by a vacuum control signal taken from the throttle valve. With a high vacuum signal (at idle or partial load), the air is diverted by the switching valve to the catalytic converter. With a low vacuum signal (under acceleration or full load), the switching valve diverts the air into the air filter housing, where it is used as regular intake air.


Check Valves
The check valves (one is located on the side of left bank valve cover below switching valve #1, the other one is located in right rear of engine below A/C compressor bracket) act as a one-way air valve. In case of a backfire or air pump failure, the valves prevents air or exhaust gases from returning into the air injection system.


Air Tube System
The air tube system feeds the air to the exhaust valves, where it is injected into the exhaust system to improve emissions output.