Nissan 240SX/Altima 1993-1998 Repair Guide

Idle Air Control Valve-Air Regulator

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OPERATION



The Idle Air Control Valve (IACV)-air regulator consists of either a wax or bimetallic spring temperature sensing mechanism and a spring. When the engine is cold, the air bypass port is open. This provides for fast idle setting while the engine heats. As the engine warms, the temperature mechanism is operated and the air bypass port closes to decrease idle speed.

TESTING



Altima

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Immerse the IACV-air regulator in cold or hot water to test its function

  1. Remove the IACV-air regulator from the engine.
  2.  
  3. Immerse the IACV-air regulator in cold or hot water.
  4.  
  5. Insert a thermometer into the water and heat or cool it, as necessary, to reach the proper testing temperatures.
  6.  
  7. Check for air flow through the valve when the water temperature is approximately 68°F (20°C).
  8.  
  9. Almost no air should flow through the valve with the water temperature at 176°F (80°C).
  10.  
  11. If the IACV-air regulator does not respond as specified, it may be faulty.
  12.  

240SX

See Figure 2



Click image to see an enlarged view

Fig. Fig. 2: On 1995-98 240SX models, measure the resistance between these terminals on the air regulator

  1. Disconnect the electrical harness from the valve.
  2.  
  3. Remove the valve and inspect the plunger for seizing or sticking. Inspect the spring.
  4.  
  5. On 1993-94 models, measure the resistance between the terminals of the valve.
  6.  
  7. On 1995-98 models, measure the resistance between the illustrated terminals.
  8.  
  9. Resistance should be 70-80 ohms @ 77°F (25°C).
  10.  
  11. If resistance is not within specification, the valve may be faulty.
  12.  
  13. If resistance is within specification, check the circuits back to the ECM.
  14.  

REMOVAL & INSTALLATION



See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: The IACV-Auxiliary Air Control (1), IACV-FICD valve (2) and IACV-air regulator (3) are located at the end of the cylinder head

The IACV-air regulator is located at the end of the cylinder head.

  1. Disconnect the electrical harness from the valve, as required.
  2.  
  3. Remove the air hoses, as required.
  4.  
  5. Remove the mounting bolts.
  6.  
  7. Remove the air regulator from the intake manifold.
  8.  

To install:
  1. Inspect the air regulator function. Check the valve for clogging and ensure that the spring has tension.
  2.  
  3. Install the air regulator on the intake manifold and tighten the bolts to 56-66 inch lbs. (6-7 Nm).
  4.  
  5. Install the air hoses, as required.
  6.  
  7. Connect the electrical harness to the valve.
  8.  

 
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