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.
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HOMESERVICE MANUALSMAZDA1991929 BASEREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/O CODESFAILS EMISSION TEST
1991 Mazda 929 Base
Fails Emission Test
1991 Mazda 929 BaseSECTION Fails Emission Test
- Ensure exhaust system is not restricted.
- Check EGR valve and solenoid for correct operation.
- Check fuel-cut system for malfunction. Fuel-cut system includes: throttle body dashpot unit, throttle position sensor and coolant thermosensor.
- Check No. 1 and No. 2 purge control valve operation.
- Check vacuum switching valve operation.
- Check secondary air injection system (B2200 and RX7).
- Check airflow meter for cracks.
- Verify correct airflow meter operation and resistance value.
- Check atmospheric pressure sensor.
- Check air valve and ISC switch.
- Ensure fuel system pressure is correct.
- Verify intake air system and throttle body electrical connections.
- Check pressure regulator and pressure regulator solenoid.
- Check water and intake air thermosensors.
- Verify throttle position sensor adjustment.
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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.