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Home >> Nissan-Datsun >> 1991 >> Sentra SE-R >> Repair and Diagnosis >> Engine Performance >> Engine Controls - Adjustments >> Adjustment >> 4-Cylinder Idle Mixture >> Pickup
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4-Cylinder Idle Mixture: Pickup

  1. Start engine and warm to normal operating temperature. Run engine at 2000 RPM for 2 minutes. Perform self-diagnostic procedure. See G - TESTS W/ CODES article. Check for smooth engine operation.
  2. Check idle speed and ignition timing. With idle speed and ignition timing correctly set, locate ECU under passenger's seat.
  3. Increase engine speed to 2000 RPM for another 2 minutes. If Green LED on ECU DOES NOT go on and off more than 5 times during 10 seconds with engine running at 2000 RPM, go to step 5).
  4. If Green LED goes on and off more than 5 times during 10 seconds with engine running at 2000 RPM, enter and set self-diagnostic system to Mode II. Red and Green LEDs on ECU should blink, simultaneously. If both LEDs blink, idle mixture is correct. If both LEDs do not blink simultaneously, go to step 7).
  5. Turn off engine and disconnect negative battery cable. Disconnect oxygen sensor and wiring harness from ECU. Using a jumper wire, ground wiring harness at oxygen sensor connector.
  6. Check continuity between terminal No. 19 of ECU wiring harness connector and ground. If continuity exists, remove jumper wire. Reconnect ECU and go to next step. If no continuity exists, repair wiring harness. After repairs, reconnect negative battery cable. Recheck idle speed and ignition timing.
  7. Disconnect engine (coolant) temperature sensor. Connect a 2500-ohm resistor to engine (coolant) temperature sensor wiring harness. Disconnect Air Induction Valve (AIV) and plug AIV pipe. Reconnect negative battery cable.
  8. Start engine and warm to normal operating temperature. Increase engine speed to 2000 RPM, 2 or 3 times. Check idle mixture (CO% level). See 4-CYLINDER IDLE SPEED & CO LEVEL  table.
  9. If idle mixture (CO% level) is incorrect, go to next step. If idle mixture (CO% level) is correct, replace oxygen sensor. If Green LED on ECU goes on and off more than 5 times during 10 seconds with engine running at 2000 RPM, recheck idle speed and ignition timing. If Green LED does not perform as indicated, go to next step.
  10. Reconnect oxygen sensor. Perform self-diagnosis and repair procedures for fuel pressure regulator, airflow meter, injectors, and engine (coolant) temperature sensor. See G - TESTS W/ CODES article.
  11. After checking idle mixture, turn off engine. Remove 2500-ohm resistor from engine (coolant) temperature sensor wiring harness and reconnect sensor. Reconnect AIV hose to pipe.
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