Nissan Maxima 1993-1998 Repair Guide

Idle Speed and Mixture Adjustments

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See Figure 1

These vehicles use a complex electronic fuel injection system which is controlled by a series of temperature and air flow sensors which feed information into an Engine Control Module, or ECM. The ECM regulates ignition timing and fuel delivery based on the input of the engine sensors to achieve maximum performance and fuel economy.

The idle speed on these vehicles is set at the factory, and does not normally require adjustment. If the vehicle is not idling correctly, Driveability & Emissions Controls to diagnose faulty components. The following procedures are included to reset the idle speed if the throttle body has been replaced.



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Fig. Fig. 1: The vehicle emission control information sticker, usually on the inner hood panel, contains vital information for tune-ups

IDLE SPEED ADJUSTMENT



VG30E Engines

See Figures 2 and 3

  1. Be sure all accessories (air conditioning, heater blower motor, radio, etc.) are off and the steering centered, with both manual and automatic transaxle models in the N position. Be sure to block the wheels and set the parking brake. Be sure the radiator cooling fan is off while checking and/or adjusting the timing and idle speed. As the load on the electrical system is increased, engine speed is affected.
  2.  
  3. Before adjusting the idle speed, visually check the following items first: air cleaner for being clogged, hoses and ducts for leaks, EGR valve for proper operation, all electrical connectors, gaskets and idle switch.
  4.  
  5. Start the engine and warm it to operating temperature, until water temperature indicator points to the middle of the gauge.
  6.  
  7. Then race the engine to 2000-3000 rpm a few times and then allow it to idle for one minute.
  8.  
  9. Check the ignition timing and adjust if necessary.
  10.  
  11. Close the Auxiliary Air Control (AAC) valve by turning the diagnostic mode selector on the ECM fully clockwise.
  12.  



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Fig. Fig. 2: Turn the diagnostic test mode selector fully clockwise before adjusting the idle speed

  1. Correct the idle speed by turning the idle speed adjusting screw.
  2.  



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Fig. Fig. 3: The idle adjustment screw is on the IACV-AAC valve on VG30E engine

  1. Operate the Auxiliary Air Control (AAC) valve by turning the diagnostic mode selector on the ECM fully counterclockwise and recheck the idle speed.
  2.  
  3. Run the engine at approximately 2000 rpm for about 2 minutes.
  4.  
  5. Verify that the idle speed is correct. If not, there may be faulty components within the engine management system. Refer to Driveability & Emissions Controls for diagnostic procedures.
  6.  

VE30DE Engines

See Figures 4, 5 and 6

  1. Be sure all accessories (air conditioning, heater blower motor, radio, etc.) are off and the steering centered, with both manual and automatic transaxle models in the N position. Be sure to block the wheels and set the parking brake. Be sure the radiator cooling fan is off while checking and/or adjusting the timing and idle speed. As the load on the electrical system is increased, engine speed is affected.
  2.  


CAUTION
The radiator cooling fan may cycle during this procedure. Be sure to keep your hands and tools away from the fan blades.

  1. Before adjusting the idle speed, visually check the following items first: air cleaner for being clogged, hoses and ducts for leaks, EGR valve for proper operation, all electrical connectors, gaskets and idle switch.
  2.  
  3. Unplug the Idle Air Control Valve/Auxiliary Air Control (IACV-AAC) valve harness connector and the Throttle Position Sensor (TPS) harness connector.
  4.  



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Fig. Fig. 4: The AICV-AAC valve should be unplugged when checking and adjusting the idle speed



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Fig. Fig. 5: The throttle position sensor should also be disconnected when checking and adjusting the idle speed

  1. Start the engine and warm it to operating temperature (water temperature gauge indicator needle in the middle).
  2.  
  3. Race the engine 2-3 times (at 2000-3000 rpm) and them let it idle for one minute. The idle speed should be within the specifications of the Tune-up Specifications Chart. To correct the idle speed, turn the idle speed adjustment screw.
  4.  



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Fig. Fig. 6: Idle speed adjustment screw location-VE30DE engine

  1. Turn the engine off and plug in the IACV-AAC valve and TPS harness connectors.
  2.  
  3. Start the engine and race it 2-3 times (at 2000-3000 rpm) and then let it idle for one minute.
  4.  
  5. Check that the idle speed is correct. If idling problems persist, refer to Driveability & Emissions Controls to diagnose the electronic engine control system.
  6.  

VQ30DE Engines

See Figure 7

  1. Be sure all accessories (air conditioning, heater blower motor, radio, etc.) are off and the steering centered, with both manual and automatic transaxle models in the Neutral position. Be sure to block the wheels and set the parking brake. Be sure the radiator cooling fan is off while checking and/or adjusting the timing and idle speed. As the load on the electrical system is increased, engine speed is affected.
  2.  


CAUTION
The radiator cooling fan may cycle during this procedure. Be sure to keep your hands and tools away from the fan blades.

  1. Before adjusting the idle speed, visually check the following items first: air cleaner for being clogged, hoses and ducts for leaks, EGR valve for proper operation, all electrical connectors, gaskets and idle switch.
  2.  
  3. Unplug the Throttle Position Sensor (TPS) connector.
  4.  
  5. Start the engine and warm it to operating temperature (water temperature gauge indicator needle in the middle).
  6.  
  7. Race the engine 2-3 times (at 2000-3000 rpm) and them let it idle for one minute. The idle speed should be within the specifications of the Tune-up Specifications Chart. To correct the idle speed, turn the idle speed adjustment screw.
  8.  



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Fig. Fig. 7: Idle speed adjustment screw location-VQ30DE engine

  1. Turn the engine off and plug in the TPS connector.
  2.  
  3. Start the engine and race it 2-3 times (at 2000-3000 rpm) and then let it idle for one minute.
  4.  
  5. Check that the idle speed is correct. If necessary, refer to Driveability & Emissions Controls to diagnose the electronic engine control system.
  6.  

MIXTURE ADJUSTMENT



See Figure 8

The air/fuel mixture is controlled by the ECM, and adjustment is not necessary or possible.



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Fig. Fig. 8:

 
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