Nissan 240SX/Altima 1993-1998 Repair Guide

Idle Air Control Valve-Auxiliary Air Control

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OPERATION



The Idle Air Control Valve-Auxiliary Air Control (IACV-AAC) functions by using a duty cycle (on/off/on), which is controlled by the ECM. The longer the "on" pulse, the greater the amount of air that will flow through the valve. The more air that flows through the valve, the higher the engine speed. Actual idle speed is the lowest speed at which the engine can operate steadily. This is computed by the ECM, taking into consideration various conditions such as warm-up, deceleration and engine load.

TESTING



See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: IACV-ACC valve terminal identification-Altima

  1. Disconnect the electrical harness from the valve.
  2.  
  3. On 21SX models, measure the resistance between the terminals of the valve.
  4.  
  5. On Altima models, measure the resistance between the illustrated connector terminals.
  6.  
  7. Resistance should be 10 ohms @ 77°F (25°C).
  8.  
  9. If resistance is not within specification, the valve may be faulty.
  10.  
  11. If resistance is within specification, check the circuits back to the ECM.
  12.  

REMOVAL & INSTALLATION



The idle air control valve is located on the underside of the intake manifold.

  1. Disconnect the electrical harness from the valve.
  2.  
  3. Remove the valve attaching bolts.
  4.  
  5. Remove the valve from the assembly.
  6.  

To install:
  1. Install the valve on the assembly.
  2.  
  3. Tighten the attaching bolts securely.
  4.  
  5. Connect the electrical harness to the valve.
  6.  

 
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