Air is drawn from clean side of air cleaner by air pump and directed under pressure to air control valve. The No. 1 relief valve of air control valve diverts part of air pump air back to air pump when engine is operating under heavy load conditions. The No. 2 relief valve of air control valve regulates the amount of air injected, based upon intake manifold vacuum and coolant temperature. The air switching valve of air control valve (if equipped) directs fresh air from air pump either "upstream" to exhaust ports and/or "downstream" to catalytic converter according to intake manifold vacuum and coolant temperature.

The air injection system contains thermo valves, delay valves, check valves and vehicle speed sensors to control and protect the air injection system. These additional components ensure fresh air is directed at the correct time and at the correct place (exhaust manifold, air cleaner, catalytic converter).

NOTE: See "Mazda Piston Engine Vacuum Diagrams" article in this section for diagram of air injection system used by model application.

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.

Safety Warning

Air Injection: Operation

Use the Manual With the Right Hardware

When to See a Mechanic

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