FixVault
Home › Nissan-Datsun › 1985 › Stanza GL, Automatic › Repair and Diagnosis › Engine Performance › System › EFI Control System › Testing & Diagnosis › Mixture Ratio Control

Mixture Ratio Control

  1. Visually check the air cleaner, hoses and ducts, EGR valve operation, electrical connectors, gaskets and throttle valve and switch. Start engine and warm up until water temperature indicator points to the middle of the gauge.
  2. Run engine at no-load at 2000 RPM for about 2 minutes. Perform EFI self-diagnosis. Repair or replace components as necessary. If engine does not run smoothly, clean and inspect injectors and replace if necessary.
  3. If engine runs smoothly, disconnect distributor vacuum hose from distributor and plug hose. Run engine at 2000 RPM for about 2 minutes under no-load. Run engine at idle speed and make sure the engine speed is below 1000 RPM. Race engine 2 or 3 times under no-load and run engine for about 1 minute at idle speed.
  4. Check ignition timing. Timing should be within 2° of TDC. If not okay, adjust and return to step 3). If okay, connect distributor vacuum hose.
  5. Run engine under no-load at about 2000 RPM for about 2 minutes. Make sure that even if Red lamp goes on, Green lamp on control unit goes on and off more than 9 times during 10 seconds at 2000 RPM. If not, go to step 8). If okay, go to next step.
  6. Race engine 2 or 3 times under no-load and then run engine at idle speed. Check inspection lamp for Red and Green blinking simultaneously. If they don't, go to step 13). If they do, again race engine 2 or 3 times under no-load and then run engine at idle speed.
  7. Check idle speeds against those listed in idle speeds table. If okay, test is complete. If no good, adjust.
    IDLE SPEEDS

    Application RPM
    M/T 650-850
    A/T In Drive 600-800
  8. If lights did not flash as listed in step 5), turn off engine and disconnect battery ground cable. Disconnect 20-pin connector from control unit. Disconnect exhaust gas sensor harness connector and connect terminal for exhaust gas sensor to ground with a jumper wire. Check for continuity between terminal 4 of 20-pin connector and ground metal of vehicle body. See Fig 1 .
    Fig 1: EFI Control Unit 20-Pin Connector Terminal Locations
    G42783
  9. If continuity does not exist, repair or replace harness and return to step 1). If continuity exists, connect 20-pin connector and battery ground. Disconnect jumper wire. Disconnect engine coolantC temperature sensor harness connector. Connect a 2500 ohm resistor between harness connector terminals.
  10. Start engine and warm up until water temperature indicator points to the middle of the gauge. Race the engine 2 or 3 times under no-load, and run at idle speed.
  11. Check idle CO. It should be below 5%. After checking, disconnect the resistor from terminals of temperature sensor and reconnect connector to sensor. If CO was not okay, go to step 13). If okay, go to next step.
  12. Replace exhaust gas sensor and make sure that even if Red lamp goes on, that Green inspection lamp goes on and off more than 9 times in 10 seconds when engine is run at 2000 RPM. If no good, replace control unit.
  13. If CO was not correct in step 11), connect exhaust gas sensor harness to sensor. Turn off engine and remove air flow meter from vehicle. Drill a hole in plug which seals variable resistor of air flow meter and remove seal plug. Install air flow meter on vehicle. Start engine and warm up until indicator is at middle of gauge.
  14. Adjust idle mixture ratio by turning variable resistor of air flow meter so that inspection lamps blink simultaneously. If found to be not adjustable, replace air flow meter and return to step 1). If adjustable, go to next step.
  15. Turn off engine and remove air flow meter. Install a new seal plug into variable resistor hole. Install air flow meter to vehicle and return to step 1).
About FixVault