Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Air Induction (Injection) System

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OPERATION



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Conventional air induction system without thermal or solenoid control



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Fig. Fig. 2: Air induction system with thermal vacuum control



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Fig. Fig. 3: Air induction system with solenoid control



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Fig. Fig. 4: Cross-sectional view of an air induction valve with two reed valves

The air induction system is used to send fresh secondary air to the exhaust manifold. During normal engine operation, the exhaust pressure usually pulsates in response to the opening and closing of the exhaust valves. By utilizing the vacuum created by the exhaust pulsation, secondary air can be drawn into the exhaust manifold, in proportion with the vacuum supply. The additional air helps complete the combustion of unburned emissions in the exhaust manifold, thereby reducing CO and HC emissions. The secondary air also increases the efficiency of the TWC converter, further reducing emissions.

The system consists of an air induction valve assembly, a filter, hoses and the connecting tubes. The induction valves contain either one or two reed valve assemblies. The reed valves prevent exhaust from flowing back through the system, into the air cleaner. Some early systems use a thermal vacuum valve to prevent system operation during extreme cold conditions and after the engine has reached operating temperature. Later model engines, use a solenoid, which is controlled by the ECM, to perform this function. ECM controlled systems operate only when the engine is cold or when hot and idling.

Some engines may use an addition valve assembly to prevent backfire, during the initial period of deceleration. This valve is known as the Anti-backfire (AB) valve.

TESTING



Anti-Backfire (AB) Valve

See Figures 5 and 6



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Fig. Fig. 5: Cross-sectional view of the AB valve assembly



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Fig. Fig. 6: Cover the passage shown when testing the anti-backfire valve

  1. Warm the engine to normal operating temperature.
  2.  
  3. Disconnect the hose from the air cleaner and place a finger near the outlet.
  4.  
  5. Run the engine at about 3000 rpm under no load, then return to idle. A suction should be felt. If no vacuum is felt, replace the AB valve.
  6.  

Air Induction Valve (AIV)
MODELS WITHOUT AIV CONTROL SOLENOID

Disconnect the air induction tube from the tube leading to the exhaust manifold. Place the tube to your mouth, then suck on the tube (air should move freely through the valve); try to blow through the tube (air should not flow through it). If the valve does not respond correctly, replace it.

MODELS WITH AIV CONTROL SOLENOID

See Figures 7 and 8



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Fig. Fig. 7: Vacuum controlled air induction valve port identification-CA18DE engine shown, others similar



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Fig. Fig. 8: Vacuum controlled air induction valve testing-CA18DE engine shown, others similar

  1. Check the air valve and control valve for binding or damage. Repair or replace the valve, if required.
  2.  
  3. Disconnect the injection hose. At the exhaust tube side, suck and blow into the hose and make sure that air flow does not exist.
  4.  
  5. Connect a vacuum pump to the air injection control valve located at the bottom of the valve case.
  6.  
  7. With vacuum applied to the valve, repeat Step 1. Air should flow freely to the exhaust pipe, and should not flow in the opposite direction.
  8.  
  9. If the valve fails to perform as specified replace the AIV valve assembly.
  10.  

AIV Control Solenoid

See Figures 9 and 10



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Fig. Fig. 9: AIV control solenoid vacuum port and electrical terminal identification-early design solenoid



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Fig. Fig. 10: AIV control solenoid vacuum port and electrical terminal identification-1991-93 vehicles

  1. Mark and tag all vacuum lines attached to the control valve. Once marked, remove the hoses from the control assembly.
  2.  
  3. Apply 12V to terminal 2 , and ground to terminal 1 .
  4.  
  5. With the solenoid energized, check for air passage between vacuum fittings as follows:

    Ports A and B-Passage open-air should pass freely
     
    Ports B and C-Passage blocked-no air should not pass
     

  6.  

  1. Disconnect the 12V power supply. With the solenoid de-energized check for air passages between the vacuum fittings as follows:

    Ports A and B -Passage blocked-no air should not pass
     
    Ports B and C -Passage open-air should pass freely
     

  2.  

  1. If the solenoid did not perform as specified, replace the EGR/EVAP solenoid/valve assembly.
  2.  

AIV Thermal Vacuum Valve
  1. Remove the thermal vacuum valve from the engine.
  2.  
  3. Plug one of the vacuum ports.
  4.  
  5. Apply vacuum to the air cleaner port; it should allow vacuum to pass. Repeat the test for other port. If either port was closed, replace the vacuum valve.
  6.  


WARNING
Do not allow water to enter the vacuum passages when testing, or the valve may be damaged.

  1. Place the valve in a container of water with a thermometer. Heat the water and Repeat Steps 2 and 3. Observe the valve operation at the following temperature.

    Below 59°F (15°C)-valve should be closed (vacuum should not pass)
     
    Between 59-140°F (15-60°C)-valve should be open (vacuum should pass)
     
    Above 140°F (60°C)-valve should be closed (vacuum should not pass)
     

  2.  
  3. If the thermal vacuum valve did not perform as specified, replace the valve.
  4.  

 
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