Air Injection: Description and Operation

This vehicle is equipped with an Air Pump that injects air into the exhaust to reduce the emissions during engine warm-up. The air injected into the exhaust will cause the catalytic converters to heat up more quickly. This will improve the emission levels during a cold start. The Air Pump Switchover System incorporates an Air Pump (4) with two Air Pump Switchover Valves (1 and 6), an Air Pump Switchover Solenoid (3), an Air Pump Relay, a Vacuum Check Valve (5) and the PCM.

The Air Pump Relay is located in the Relay Control Module and can be easily identified by referring to the relay control module label. The Air Pump is mounted to the top center of the engine timing cover. The Air Pump Switchover valves (1 and 6) are located at the front, top of the engine, mounted just in front of the left and right cylinder covers. The Air Pump Switchover Solenoid (3) is mounted on the right front of the engine, just below the Air Pump Switchover Valve RH (6).




Air is allowed to enter the exhaust when the PCM simultaneously actuates the Air Pump Relay, Air Pump (1), and Air Pump Switchover Solenoid (4) after engine start-up for up to 2 1/2 minutes. The following conditions must also be met in order for the system to become active:
- Coolant Temperature >10° C (50° F) but <60° C (140° F)
- Engine Speed <3000 RPM
- Throttle Valve Not Wide Open

After an actuation, the air injection system will remain deactivated until the coolant temperature drops from >60° C (140° F) to <40° C (104° F).

The Air Pump (1) draws in air through a maintenance-free filter and pumps it to the Air Pump Switchover Valves (3 and 6). The Air Pump Switchover Valves (3 and 6) prevent exhaust gases from flowing back into the Air Pump (1). The Air Pump Switchover Solenoid (4) is supplied with vacuum from the intake manifold through a check valve (5). When the Air Pump Switchover Solenoid (4) is activated, it passes engine vacuum to the Air Pump Switchover Valves (3 and 6). The air which is delivered via the Air Pump Switchover Tube (2) is forced through the valves into the cylinder head openings to the exhaust. The injected air reacts with the hot exhaust gases in the outlet port. An oxidation of carbon monoxides (CO) and hydrocarbons (HC) takes place and results in an additional increase in the exhaust temperature.