Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Air Injection: Operation
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 startup 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.
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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