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HOMESERVICE MANUALSAUDI1996A4 BASE, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/O CODESSYMPTOMSFAILS EMISSION TEST
1996 Audi A4 Base, Standard

Fails Emission Test

1996 Audi A4 Base, StandardSECTION Fails Emission Test
  • Ensure engine is at normal operating temperature.
  • Check crankcase for fuel contamination.
  • Ensure base timing is correct.
  • Check for correct PCV valve operation.
  • Check EGR system for correct operation.
  • Check Mass Airflow (MAF) sensor.
  • Ensure air intake system is not restricted.
  • Check vapor recovery system operation.
  • Check Engine Coolant Temperature (ECT) sensor operation.
  • Check Heated Oxygen Sensor (HO2S) output voltage.
  • Ensure fuel system pressure is correct.
  • Check fuel tank filler tube for tampering of restrictor. If tampering has occurred, check catalytic converter for lead contamination and exhaust system restriction.
  • Check for poor quality fuel containing insufficient cleaning additives.
NOTE: Prolonged use of poor quality fuel can cause injector clogging and carbon build-up on intake system.
RENDER: 1.0x

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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.