Toyota Pick-ups/Land Cruiser/4Runner 1989-1996

Air Injection System

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OPERATION



See Figures 1, 2, 3 and 4

This system is used on the 22R and 3F-E engines only.

Some unburned HC and CO remains in the exhaust flow after it leaves the cylinder. To encourage further burning in the exhaust port, compressed air from the air pump is blown into the exhaust port. This generally takes place during low and medium speed driving or during high speed deceleration. The engine control computer uses input signals from the rpm, the coolant temperature sensor and the engine vacuum sensor to control the function of the Vacuum Solenoid Valve (VSV). The VSV acts as a gatekeeper for the system, turning it on and off by controlling vacuum. Within the system, further control is maintained by both the Air Bypass and Air Switching Valves (ABV/ASV).



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Fig. Fig. 1: Air injection system components-22R engine



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Fig. Fig. 2: Air injection system schematic-22R engine



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Fig. Fig. 3: Air injection system components-3F-E engine



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Fig. Fig. 4: Air injection system schematic-3F-E engine

TESTING



Air Pump

Do not hammer, pry, or bend the pump housing while tightening the drive belt or testing the pump.

BELT TENSION AND AIR LEAKS
  1. Before proceeding with the tests, check the pump drive belt tension to ensure that it is within specifications.
  2.  
  3. Turn the pump by hand. If it has seized, the belt will slip, making a noise. Disregard any chirping, squealing, or rolling sounds from inside the pump; these are normal when it is turned by hand.
  4.  
  5. Check the hoses and connections for leaks. Hissing or a blast of air is indicative of a leak. Soapy water, applied lightly around the area in question, is a good method for detecting leaks.
  6.  

AIR OUTPUT
  1. Disconnect the air supply hose at the anti-backfire valve.
  2.  
  3. Attach a vacuum gauge, using a suitable adaptor, to the air supply hose.
  4.  

If there are two hoses, plug the second one.

  1. With the engine at normal operating temperature, increase the idle speed and watch the vacuum gauge.
  2.  
  3. The air flow from the pump should be steady and fall between 2-6 psi. (14-41 kPa). If it is unsteady or falls below this, the pump is defective and must be replaced.
  4.  

PUMP NOISE DIAGNOSIS

The air pump is normally noisy; as engine speed increases, the noise of the pump will rise in pitch. The rolling sound the pump bearing make is normal. But if this sound becomes excessive at certain speeds, the pump is defective and will have to be replaced.

A continual hissing sound from the air pump pressure relief valve at idle, indicates a defective valve. Replace the relief valve.

If the pump rear bearing fails, a continual knocking sound will be heard. Since the rear bearing is not separately replaceable, the pump will have to be replaced as an assembly.

Anti-Backfire Valve (ABV)

The ABV is easily checked with the engine running at idle. Disconnect the small vacuum hose from the valve, then reconnect it. At the time of reconnection, check the end of the large output hose; a momentary burst of compressed air from the pump should be felt.

Check Valve
  1. Remove the check valve.
  2.  
  3. Blow into the manifold side (large side) and check that the valve is closed.
  4.  
  5. Blow into the ASV side (small side) and check that the valve is open.
  6.  
  7. If the valve is not operating properly it requires replacement.
  8.  

Air Switching Valve (ASV)

  1. Disconnect the air bypass hose from the air cleaner.
  2.  
  3. With the engine coolant cold, below 43°F (6°C), start the engine and check that air is discharged from the bypass hose.
  4.  
  5. Warm up the engine to normal operating temperature. Plug the hose. Reconnect the vacuum line.
  6.  
  7. With the engine idling, check that no air comes out of the bypass hose.
  8.  
  9. Race the engine momentarily and quickly release the throttle; air should be momentarily discharged from the bypass hose.
  10.  
  11. Increase the engine speed to a steady 3000 rpm; air should be discharged through the hose.
  12.  
  13. Reconnect the air hose to the air cleaner.
  14.  

Vacuum Switching Valve (VSV)

  1. Disconnect the hose between the VSV and the ASV at the VSV side.
  2.  
  3. Connect a vacuum gauge to the VSV port.
  4.  
  5. Run the engine at 4800 rpm; the gauge should read zero.
  6.  
  7. Pinch the hose between the vacuum switch and the air pipe.
  8.  
  9. Again increase engine speed to 4800 rpm; the gauge should indicate manifold vacuum.
  10.  
  11. Disconnect the vacuum gauge and reconnect the hose to the VSV.
  12.  

REMOVAL & INSTALLATION



Air Pump
  1. Label and disconnect the air hoses from the pump.
  2.  
  3. Loosen the bolt on the adjusting link and remove the drive belt.
  4.  
  5. Remove the mounting bolts and withdraw the pump.
  6.  

To install:

Do not pry on the pump housing, it may become distorted.

  1. Attach the air pump to the vehicle with the mounting bolts. Tighten the bolts until snug.
  2.  
  3. Adjust the drive belt tension after installation.
  4.  
  5. Attach the hoses to the pump.
  6.  
  7. Start the engine and check for proper operation.
  8.  

 
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