Nissan Pick-ups and Pathfinder 1970-1988

Air Induction System

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OPERATION



See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10

Gasoline Engines Only

The air induction system is designed to send secondary air to the exhaust manifold, utilizing a vacuum caused by exhaust pulsation in the exhaust manifold.

The pressure in the exhaust manifold usually pulsates in response to the opening and closing of the exhaust valve. It decreases below atmospheric pressure periodically.

If a secondary air intake pipe is opened to the atmosphere under vacuum conditions, secondary air can be drawn into the exhaust manifold in proportion to the vacuum.

Therefore, the air induction system reduces CO and HC emissions in exhaust gases. The system consists of two air induction valves, a filter, hoses and E.A.I. tube(s).

AIR INDUCTION VALVE CASE

The air induction valve case consists of 2 reed valves, a rubber seal and a filter. The valve case is attached to the air cleaner. There are 2 types of air induction valve cases. Type A is equipped with 2 hose connectors and is installed on California models, while Type B is equipped with 1 connector and is installed on non-California models.

AIR INDUCTION VALVE

Two reed valve type check valves are installed in the air cleaner. When the exhaust pressure is below atmospheric pressure (negative pressure), secondary air is sent to the exhaust manifold.

When the exhaust pressure is above atmospheric pressure, the reed valves prevent secondary air from being sent back to the air cleaner.

AIR INDUCTION VALVE FILTER

The air induction valve filter is installed at the dust side of the air cleaner. It purifies secondary air to be sent to the exhaust manifold.

AIR INDUCTION PIPE

The secondary air fed from the air induction valve goes through the Exhaust Air Injection (EAI) pipe to the exhaust manifold.

at this point, the mixture in the intake manifold becomes too rich to ignite and burn in the combustion chamber and burns easily in the exhaust system with injected air in the exhaust manifold.

The Anti-backfire (AB) valve provides air to the intake manifold to make the air/fuel mixture leaner and prevents backfire.

The correct function of this valve reduces hydrocarbon emission during deceleration.

SERVICE



Air Induction Valve and Filter

Remove the valve and filter on the air cleaner. The air induction valve and valve filter can then be taken out easily. Installation is in the reverse sequence of removal.

AB Valve
  1. Remove air cleaner.
  2.  
  3. Remove air hoses and vacuum tube. Then the AB valve can be taken out.
  4.  



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Fig. Fig. 1: California type air induction case



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Fig. Fig. 2: 49 States type air induction case



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Fig. Fig. 3: Air induction valve



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Fig. Fig. 4: Air induction filter



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Fig. Fig. 5: Checking the AB valve-1985-86 Z20 and Z24 engines



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Fig. Fig. 6: Checking the AB valve-1986-88 Z24i engines



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Fig. Fig. 7: Checking the AB valve-1986-88 VG30i engines



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Fig. Fig. 8: Exploded view of the air box-1986-88 Z24i engines (2wd)



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Fig. Fig. 9: Exploded view of the air box-1986-88 Z24i engines (4wd)



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Fig. Fig. 10: Exploded view of the air box-1986-88 VG30i engines

 
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