Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Idle Air Adjusting (IAA) Unit

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OPERATION



See Figures 1, 2 and 3



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Fig. Fig. 1: Idle Air Adjusting Unit component identification-GA16i engine



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Fig. Fig. 2: Idle Air Adjusting Unit component identification-1991-94 GA16DE and all SR20DE engines



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Fig. Fig. 3: IACV-AAC mounting location-1995-96 GA16DE engine

GA16i, CA16DE, CA18DE, GA16DE and SR20DE engines all use the Idle Air Adjusting (IAA) Unit to maintain the idle speed at a predetermined range. The IAA unit is made up of Fast Idle Control Device (FICD) solenoid valve and the Auxiliary Air Control (AAC) valve. Only the GA16i engine uses an Idle-up solenoid.

The Auxiliary Air Control valves are used to control the engine idle speed, by regulating the amount of air flow allowed to bypass the throttle plates. The valve assembly is controlled by on/off pulses received from the ECM. By energizing the valve longer, more air will bypass the throttle plates, thus the engine speed will increase.

The FIC system is used to bypass additional air, when the AAC valve may not be able to compensate. The FICD solenoid is energized, when an additional load is placed on the engine, such as; high power steering effort or when the A/C compressor clutch is engaged. The GA16i engine uses both a FICD and an Idle-up solenoid to perform this function.

TESTING



Auxiliary Air Valve (AAV)
EXCEPT 1995-96 1.6L (GA16DE) ENGINE

See Figures 4 and 5



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Fig. Fig. 4: Exploded view of the AAC valve assembly-1991-94 GA16DE and SR20DE engines



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Fig. Fig. 5: AAC valve mounting location-GA16i engine

  1. Disconnect the IAC auxiliary air control harness connector.
  2.  
  3. Measure resistance between the IAC auxiliary air control terminals. The resistance should be approximately 10 ohms.
  4.  

If resistance is not within specifications, replace the IAC control valve

  1. Visually inspect the valve plunger for sticking or binding. Check the valve spring for damage and replace if necessary.
  2.  

1995-96 1.6L (GA16DE) ENGINE

See Figure 6



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Fig. Fig. 6: IACV-AAC valve terminal identification-1995-96 GA16DE engine

  1. Disconnect the electrical connector from the IACV-AAC valve.
  2.  
  3. Connect an ohmmeter across AAC valve terminals 2 and 3 . Measure the resistance across the terminals.
  4.  
  5. Connect an ohmmeter across AAC valve terminals 3 and 4 . Measure the resistance across the terminals.
  6.  
  7. The resistance measurement in both tests should be 50-100 ohms at 77°F (25°C). If the resistance is not within specifications, replace the IACV-AAC valve assembly.
  8.  

Fast Idle Control Device (FICD) and Idle-up Valve
EXCEPT 1995-96 1.6L (GA16DE) ENGINE

See Figures 7, 8 and 9



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Fig. Fig. 7: Connect a battery to the FICD solenoid valve, as shown-1991-94 GA16DE engine shown, SR20DE engine similar



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Fig. Fig. 8: Exploded view of the FICD solenoid valve assembly-1991-94 GA16DE and SR20DE engines



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Fig. Fig. 9: FICD and Idle-up solenoid connector terminal identification-GA16i engine

  1. Unplug the harness connector.
  2.  

On the GA16i engine, make certain to properly identify the connector terminals before applying voltage to the valve. All other engines will use a two terminal connector.

  1. Apply 12V to the harness connector terminals (IAA unit side). On GA16i engines, use terminals A and B for FICD testing and terminals C and D for Idle-up solenoid testing.
  2.  
  3. Listen for a clicking sound when 12V is applied.
  4.  
  5. If no sound is present, check the plunger for sticking or a broken spring.
  6.  

1995-96 1.6L (GA16DE) ENGINE

See Figure 10



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Fig. Fig. 10: IACV-FICD solenoid valve terminal identification-1995-96 GA16DE engine

  1. Disconnect the electrical connector from the IACV-FICD solenoid.
  2.  
  3. Connect an ohmmeter across FICD solenoid terminals 1 and 5 .
  4.  
  5. Measure the resistance across the terminals. Resistance should be 75-125 ohms. If the resistance is not within specifications, replace the IACV-FICD solenoid assembly.
  6.  

REMOVAL & INSTALLATION



See Figures 11 and 12



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Fig. Fig. 11: Detach the electrical connector from the FICD solenoid



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Fig. Fig. 12: Remove the IAA unit from the intake manifold by unfastening the mounting bolt and nut

  1. Disconnect the harness connector from the idle air adjusting unit.
  2.  
  3. Unfasten the retaining bolts securing the IAA unit to the intake manifold, and remove the unit.
  4.  
  5. Remove any gasket material from the mating surface.
  6.  

To install:
  1. Position the IAA unit to the intake. Using a new gasket on the engine and secure with the retaining bolts.
  2.  
  3. Connect the wiring harness to the IAA unit.
  4.  

ADJUSTMENT



The IAC auxiliary air control and the IAC valve fast idle control device are mounted on a common component called the idle air adjusting unit (IAA). The fast idle speed is adjusted by turning the idle adjusting screw which is located on the idle air adjusting unit. See Routine Maintenance for more specific information.

 
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