Nissan Pick-ups and Pathfinder 1989-1995

Air Induction Valve (AIV) System



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 exhaust pressure in the exhaust manifold usually pulsates in response to the opening and closing of the exhaust valve and 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.

On some applications, the Air Induction Valve (AIV) control solenoid and the Swirl Control Valve (SCV) solenoid cuts the intake manifold vacuum signal. These solenoids have an electrical connection and vacuum lines. If equipped in your vehicle, make sure the unit is properly mounted and all connections are properly installed.

The introduction of fresh air (oxygen) into the exhaust stream allows a further burning of the exhaust gases even after they have left the combustion chamber. In this way, the air induction system contributes to the reduction of CO and HC emissions in the exhaust gasses. The system usually consists of two air induction valves, filter hoses and routing cables.

Air Induction Valve Case

The air induction valve case is attached to the air cleaner, and consists of 2 reed valves, a rubber seal and a filter.

There are 2 types of air induction valve cases. One type is equipped with 2 hose connectors, and is installed on California models. The other type is equipped with 1 connector and is installed on non-California models.

Air Induction Valve

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

Anti-Backfire (AB) Valve

The AB valve provides air from the air cleaner to the intake manifold to prevent backfiring during deceleration.


Air Induction Valve (AIV) Case

See Figures 1, 2, 3, 4, 5 and 6

Before proceeding with any extensive testing, check the condition of the hoses and lines used. If any hoses are cracked, torn or fit loosely, replace with a new piece.

To check the AIV system, start the engine and allow it to reach a normal operating temperature. Open the hood and try to listen to the AIV unit. If it is functioning correctly, it will be emitting a low pitched buzzing sound at idle. There should be no sound above idle. Also, remove the vacuum line from the top of the AIV assembly, and check for vacuum during idle. If you place a finger over the line, you should feel a sucking motion on your finger. As noted earlier, this condition exists only at idle, not under throttle conditions.

Turn the engine OFF . With the vacuum line removed from the AIV unit, connect a vacuum pump. Remove one end of the remaining hoses from the AIV unit. Apply vacuum to the unit, while at the same time blowing into the hose. With vacuum applied, you should be able to blow through the hose without any difficulty.

One final condition to check is the voltage level. Unplug the wire harness connector from the AIV unit, and check for voltage during idle, and under throttle. At idle, there should be no voltage, while at throttle, there should be battery voltage.

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Fig. Fig. 1: Exploded view of the AIV canister assembly-4 cylinder (2WD)

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Fig. Fig. 2: Exploded view of the AIV canister assembly-4 cylinder (4WD)

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Fig. Fig. 3: Exploded view of the AIV canister assembly-6 cylinder

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Fig. Fig. 4: Air induction valve

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Fig. Fig. 5: Checking the AIV case assembly-6 cylinder engine

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Fig. Fig. 6: Checking the AIV case assembly-4 cylinder engine

Anti-Backfire (AB) Valve

See Figures 7, 8 and 9

To check the AB valve, Open the engine hood, and remove the air cleaner cover. With the filter out, and the engine running at idle, place your finger over the opening in the base of the cleaner. If the valve function correctly, there should be a sucking action under all conditions, except under throttle.

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Fig. Fig. 7: Anti-backfire valve

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Fig. Fig. 8: Checking the AB valve-6 cylinder engine

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Fig. Fig. 9: Checking the AB valve-4 cylinder engine


No adjustments are either necessary or possible to this system.


Air Induction Valve and Filter
  1. Remove the valve and filter cover on the air cleaner, by removing the retaining nuts securing the assembly.
  3. With the cover removed, the valve and parts can be accessed easily.

To install:
  1. Check the filter housing and make sure if is free of dirt and debris.
  3. Position the filter and valve in place, then install the cover and secure with the retaining nuts.

Anti-backfire (AB) Valve
  1. Remove air cleaner cover, followed by the filter.
  3. Disconnect the air hoses and vacuum tube, being careful to mark them before disassembly. Remove the AB valve from air cleaner housing assembly, by unfastening the retaining hardware.

To install:
  1. Position the AB valve to the air cleaner, and secure using the retaining hardware.
  3. Attach the hoses and vacuum line to the valve. Make sure the order is correct.
  5. Install the filter and air cleaner cover.