1990 Nissan-Datsun 240SX XE, StandardFACTORY OEM SERVICE PROCEDURE

Engine Controls - Tests W/O Codes: Backfire: Intake

  1. Ensure there are no vacuum leaks into intake system.
  2. Ensure ignition timing is within specification.
  3. Remove vacuum hose from fuel pressure regulator and monitor for symptom change. (Clean injector if improves).
  4. Enter self-diagnostic Mode II and monitor fuel metering system operation.
  5. Disconnect exhaust gas sensor and monitor change in driveability. If it improves, replace sensor. If not, go to 4.
  6. For Airflow Meter: Enter self-diagnostic Mode III and retrieve codes. If vehicle will not start, crank engine before entering self-diagnostic Mode III.
  7. For Airflow Meter: Enter self-diagnostic Mode V and monitor real-time diagnostic setting of fault codes. Perform appropriate code chart in TESTS W/CODES article.
Factory Service Tools

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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.

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