Most Mazda piston engines use the conventional air injection system. This system uses a belt-driven vane-type pump to force air through air injection nozzles into the exhaust manifold. The system employs a check valve near the exhaust manifold to keep exhaust gases from traveling back into the air lines if the air pump fails. The system also uses an air control valve which regulates the amount of air sent to the exhaust manifold, increasing it when the vehicle is overrunning (throttle closed at speeds beyond about 20 mph), at which time extra fuel is admitted to the manifold.
Various models replace the air pump with a pulse-type system which utilizes pressure waves in the exhaust system and a reed valve to pump air into the exhaust manifold. Models not using pulse air employ a conventional air pump, a catalytic converter, and a system which protects the converter from overheating by interrupting air flow at high converter temperatures.
- Disconnect the hose from the air pump outlet.
- Connect a pressure gauge to the outlet.
- Check the drive belt for proper tension, then start and run the engine at 1,500 rpm. The gauge reading should be at least 1 psi (2.04 in. Hg/52mm Hg). If not, replace the pump.
- Run the engine until it reaches normal operating temperature. Disconnect the air hose at the reed valve.
- Run the engine at idle speed, and place a finger over the inlet of the reed valve. Air should be sucked into the valve.
- Increase speed to 1,500 rpm and make sure no exhaust gas is discharged from the reed valve inlet.
- Run the engine at idle.
- At idle, no air should be felt at the relief valve. If air flow is felt, replace the valve.
- Increase the idle to 2,000 rpm on the 1.6L engine, or 4,000 rpm on other engines. If air flow is felt, the valve is working properly.
- Run the engine until it reaches normal operating temperature. Disconnect the air hose at the check valve on the exhaust manifold.
- Gradually increase the engine speed to 1,500 rpm, while carefully checking for exhaust (hot) gas leakage from the check valve. Replace the valve if exhaust gases are present.
- Start the engine and run it at idle.
- Hold a finger over the relief valve port of the air control valve. Discharge air should be felt.
- Disconnect the vacuum sensing tube from the air control valve and plug the tube. No air should be felt at the relief port.
- Disconnect the vacuum sensing tube from the air control valve solenoid.
- Blow through the vacuum tube; air should pass through the valve. Suck on the tube; no air should pass through the valve.
- Disconnect the inlet and outlet hoses at the pump.
- Unfasten the adjusting bolt and remove the drive belt.
- Support the pump and remove the mounting bolts. Lift out the pump.
- Lower the pump onto its mounting and install the retaining bolts.
- Install the drive belt onto the pulley, then insert the adjusting bolt. Adjust the drive belt to specification.
- Connect the inlet and outlet hoses to the pump.
- Disconnect the vacuum lines from the valve.
- Disconnect the wiring from the valve.
- Disconnect the air hoses from the valve.
- Unbolt and remove the valve.
- Place the valve into position and bolt it in place.
- Connect the air hoses, wiring and vacuum lines to the valve.
- Disconnect the inlet air hose.
- Unscrew the valve from the exhaust manifold.
- Screw the valve into the exhaust manifold.
- Connect the inlet air hose.