FixVault
Home › Nissan-Datsun › 1991 › Sentra SE-R › Repair and Diagnosis › Engine Performance › Engine Controls - Adjustments › Adjustment › V6 Idle Mixture › 300ZX

V6 Idle Mixture: 300ZX

  1. Start engine and warm to normal operating temperature. Run engine at 2000 RPM for 2 minutes.
  2. Perform self-diagnostic procedure. See G - TESTS W/ CODES article. Check for smooth engine operation. Check engine idle speed and timing. With idle speed and timing correctly set, locate ECU under right side of dash (behind glove box). Increase engine speed to 2000 RPM for another 2 minutes.
  3. Enter and set self-diagnostic system to Mode II. See G - TESTS W/ CODES article. Ensure Red LED on ECU goes on and off more than 5 times during 10 seconds with engine running at 2000 RPM. If not, replace left oxygen sensor and repeat idle mixture procedure. If Red LED DOES NOT come on at all, go to step 7). If Red LED operates as stated, go to next step.
    NOTE: If idle mixture is still incorrect (Red LED on ECU DOES NOT come on and off more than 5 times during 10 seconds) after replacing left oxygen sensor, perform self-diagnosis and repair procedures for fuel pressure, airflow meter, injectors and engine coolant temperature sensor.
  4. Increase engine speed to 2000 RPM, 2 or 3 times once more. Red LED on ECU should go on and off more than 5 times during 10 seconds with engine running at 2000 RPM. If not, replace right oxygen sensor and repeat test procedure starting at step 3). If Red LED DOES NOT come on at all, go to next step. If Red LED operates as stated, oxygen sensors and idle mixture are correct.
  5. Check right oxygen sensor wiring harness. To do so, turn off engine. Disconnect negative battery cable. Disconnect right oxygen sensor wiring harness connector and ECU 76-pin connector.
  6. Check continuity between terminal No. 29 of ECU 76-pin connector and center terminal of oxygen sensor wiring harness connector. If continuity exists, go to step 9). If not, repair wiring harness and repeat idle mixture procedure starting at step 3).
  7. Check left oxygen sensor wiring harness. To do so, turn off engine. Disconnect negative battery cable. Disconnect left oxygen sensor wiring harness connector and ECU 76-pin connector.
  8. Check continuity between terminal No. 55 of ECU 76-pin connector and center terminal of oxygen sensor wiring harness connector. If continuity exists, go to next step. If not, repair wiring harness and repeat idle mixture procedure starting at step 3).
  9. Reconnect ECU 76-pin connector. Disconnect engine coolant temperature sensor connector. Connect a 2500-ohm resistor to engine coolant temperature sensor wiring harness. Disconnect Air Injection Valve (AIV) wiring harness connector.
  10. Reconnect negative battery cable. Start engine and warm to normal operating temperature (coolant gauge needle in middle). Increase engine speed to 2000 RPM, 2 or 3 times, then allow engine to return to idle.
  11. Check idle mixture (CO% level). See V6 IDLE SPEED & CO LEVEL TABLE  . If idle mixture (CO% level) is correct, replace LEFT oxygen sensor and repeat procedure starting at step 3).
  12. If idle mixture (CO% level) is incorrect, reconnect oxygen sensor. Perform self-diagnosis and repair procedures for fuel pressure, airflow meter, injectors, and engine coolant temperature sensor.
  13. After checking idle mixture, turn off engine. Remove 2500-ohm resistor from engine coolant temperature sensor wiring harness and reconnect sensor. Reconnect AIV wiring harness connector.
About FixVault