After ensuring air pump and all hoses are correct, check carburetor and air control valve attaching nuts for tightness. Warm engine to normal operating temperature.
Stop engine and connect a tachometer. Disconnect air cleaner-to-air control valve hose at air cleaner. Disconnect both vacuum hoses from relief solenoid valve (Blue color dot).
Using rubber hose, by-pass relief solenoid valve by connecting vacuum lines on each side of relief valve together. See Fig 1. This will cause manifold vacuum to be routed directly to air control valve.
Start engine and run at idle. Place finger over air cleaner-to-air control valve hose and check that air is not escaping through hose. Disconnect rubber hose used to by-pass relief solenoid valve; air should escape at air cleaner-to-air control valve hose.
Reconnect by-pass hose at relief solenoid valve. Using throttle, set engine speed at 2500 RPM. Disconnect vacuum sensing tube from switching solenoid valve (Gray color dot).
Place finger over air cleaner-to-air control valve hose; air should escape through hose. Reconnect switching solenoid valve vacuum tube; air should not escape at air cleaner-to-air control valve hose. If air control valve does not respond as described, replace air control valve.

Fig 1: Hose Arrangement for Checking Air Control Valve Operation

Courtesy of MAZDA MOTORS CORP.

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 Control Valve