GM Blazer/Jimmy/Typhoon/Bravada 1983-1993 Repair Guide

Air Injection Reactor (AIR)

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OPERATION



See Figures 1, 2, 3 and 4

Many (though not all) of the vehicles covered by this guide are equipped with an Air Injector Reactor (AIR) or AIR management system. The AIR system uses an air pump, air check valve(s), a mixture control (deceleration) valve, an air switching (diverter) valve, and an air manifold (with air injector nozzles).

The air pump transmits filtered air received from the air cleaner assembly, through the air switching valve and the check valve, into an air manifold assembly which is mounted on the cylinder head. As the hot exhaust gas comes out from the combustion chamber, it meets with a blast of air from the air injection nozzle located in the exhaust port to burn some of the hydrocarbon and carbon monoxide emissions.

Upon receiving a high vacuum signal from the intake manifold, the mixture control valve introduces ambient air through the air filter into the intake manifold to dilute the momentarily rich fuel mixture that occurs on initial throttle closing. This eliminates backfire.

On most California and TBI models, the Electronic Control Module (ECM) operates an electric air control valve which directs the air flow to the engine exhaust manifold ports or the air cleaner. When the engine is cold or in wide-open throttle, the ECM energizes the solenoid to direct the air flow into the exhaust manifold check valves. When the engine warms, operating at high speeds or deceleration, the ECM de-energizes the electric air control valve, changing the air flow from the exhaust manifold to the air cleaner. On some applications, at higher engine speeds air can be rediverted back to the air cleaner through a pressure relief valve, even though the solenoid is still energized. The diversion of the air flow to the air cleaner acts as a silencer.

A check valve or valves prevents back flow of the exhaust gases into the air pump, if there is an exhaust backfire or pump drive belt failure.



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Fig. Fig. 1: AIR system - 1.9L engine



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Fig. Fig. 2: AIR system - 2.0L engine



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Fig. Fig. 3: Common AIR system for carbureted 2.8L engines



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Fig. Fig. 4: AIR system - 2.8L TBI engine

TESTING



Air Injection Pump

See Figures 5, 6 and 7

Accelerate the engine to approximately 1500 rpm and observe the air flow from hose(s). If the air flow increases as the engine is accelerated, the pump is operating satisfactorily. If the air flow does not increase or is not present, proceed as follows:

  1. Check for proper drive belt tension. The Air Management System is not completely noiseless. Under normal conditions, noise rises in pitch as the engine speed increases. To determine if excessive noise is the present, operate the engine with the pump drive belt removed. If excessive noise does not exist with the belt removed, proceed as follows:
  2.  
  3. Check for a seized Air Injection Pump. DO NOT oil the air pump.
  4.  
  5. Check the hoses, the pipes and all connections for leaks and proper routing.
  6.  
  7. Check the air control valve.
  8.  
  9. Check air injection pump for proper mounting and bolt torque.
  10.  
  11. Repair irregularities in these components, as necessary.
  12.  
  13. If no irregularities exist and the air injection pump noise is still excessive, replace the pump.
  14.  

Check Valves
  1. The check valve should be inspected whenever the hose is disconnected from the check valve or whenever a check valve failure is suspected (A pump that had become inoperative and had shown indications of having exhaust gases in the pump would indicate check valve failure).
  2.  
  3. With the check valve removed, blow through the check valve (toward the exhaust manifold side) then turn the valve around and attempt to blow back through it (toward the AIR pump). The flow should only be in one direction (toward the exhaust manifold). Replace the valve which does not function correctly.
  4.  

Air Hoses and Injection Pipes
  1. Inspect all hoses for deterioration or holes.
  2.  
  3. Inspect all air injection pipes for cracks of holes.
  4.  

When checking pipes and hoses, look at the routing. Improper positioning and interference with other components may cause wear.

  1. Check all hose and pipe connections.
  2.  
  3. Check pipe and hose routing; interference may cause wear.
  4.  
  5. If a leak is suspected on the pressure side of the system or any hose has been disconnected on the pressure side, the connection should be checked for leaks with a soapy water solution. Look for bubbles which will form at any bad connections when the pump is operating.
  6.  
  7. If a hose, manifold and/or pipe assembly replacement is required, note the routing, then replace the item as required.
  8.  
  9. When installing the new item, be sure to connect the hoses correctly.
  10.  

Air Switching (Diverter) Valve (ASV)

The diverter valve directs air to the exhaust ports unless there is a sudden rise in manifold vacuum due to deceleration. In such a case air is diverted to the intake manifold.

If the diverter valve is functioning properly, the secondary air will continue to blow out from the valve for a few seconds when the accelerator pedal is pressed to the floor and released quickly. If the secondary air continues to blow out for more than 5 seconds, replace the air switching valve.



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Fig. Fig. 5: Electric diverter valve system schematic - Early model vehicles



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Fig. Fig. 6: Electric diverter valve check - early model vehicles



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Fig. Fig. 7: Electronic air control valve schematic and check - late model vehicles

Mixture Control (Deceleration) Valve
  1. Install a tachometer to the engine and allow the engine to establish normal operating temperatures.
  2.  
  3. Remove the air cleaner and plug the air cleaner vacuum hose(s).
  4.  
  5. Operate the engine at idle speed, then remove the deceleration valve-to-intake manifold (diaphragm) hose.
  6.  
  7. Reconnect the hose and listen for a noticeable air flow (hiss) through the air cleaner-to-deceleration valve hose; there should also be a noticeable drop in idle speed.
  8.  
  9. If the air flow does not continue for at least one second or the engine speed does not drop, check the hoses (of the deceleration valve) for restrictions or leaks.
  10.  
  11. If no restrictions are found, replace the deceleration valve.
  12.  

REMOVAL & INSTALLATION



Air Injection Pump

The air pump is non-serviceable, it must be replaced as an assembly, if defective.

  1. Disconnect the negative battery cable.
  2.  
  3. Compress the drive belt to keep the pump pulley from turning, then loosen the pump pulley bolts.
  4.  
  5. Loosen the pump-to-mounting bracket retainers, release the drive belt tension, then remove or reposition the belt.
  6.  
  7. Remove the hoses, the vacuum lines, the electrical connectors (if equipped) and the air control or diverter valve.
  8.  
  9. Unscrew the mounting bolts and then remove the pulley.
  10.  
  11. Unscrew the pump mounting bolts and then remove the pump.
  12.  
  13. If necessary, use a pair of needle nose pliers to pull the filter fan from the hub.
  14.  

To install:
  1. Install the AIR pump assembly and secure using the retaining bolts.
  2.  
  3. If removed, position a new filter fan on the pump hub. DO NOT drive the filter fan on with a hammer.
  4.  
  5. Install the spacer and pump pulley against the centrifugal filter fan.
  6.  
  7. Install the pulley bolts and tighten them evenly in order to compress the centrifugal filter fan onto the pump hole. DO NOT drive the filter fan on with a hammer. A slight amount of interference with the housing bore is normal. After a new filter fan is installed it may squeal upon initial operation or until the OD of the sealing lip has properly worn in. To break in the sealing lip the engine should be operated at various engine speeds once installation is complete.
  8.  
  9. Install the hoses, vacuum, lines, electrical connectors and air control or diverter valve, as applicable.
  10.  
  11. Install the drive belt and adjust the tension (unless equipped with a serpentine belt).
  12.  
  13. Connect the negative battery cable and check for proper pump operation.
  14.  

Air Pump Drive Belt Adjustment and Replacement

Vehicles using a serpentine accessory drive belt are equipped with an automatic tensioner, no adjustment is necessary.

  1. Inspect the drive belt for wear, cracks or deterioration.
  2.  
  3. Loosen the pump adjustment and pivot bolts.
  4.  
  5. Replace the drive belt, if necessary.
  6.  

For more information regarding drive belts please refer to General Information & Maintenance in this guide.

  1. Move the air pump until the drive belt is at proper tension, then retighten bolts.
  2.  
  3. Check the drive belt tension using a belt tension gauge.
  4.  

Air Pump Pulley Replacement
  1. Hold the pump pulley from turning by compressing the drive belt, then loosen the pump pulley bolts.
  2.  
  3. Loosen the pump-to-mounting bracket retainers, release the drive belt tension, then remove or reposition the belt.
  4.  
  5. Unscrew the mounting bolts and then remove the pulley and pulley spacer.
  6.  

To install:
  1. Install the pump pulley and spacer with the retaining bolts hand-tight.
  2.  
  3. Install the drive belt and adjust (V-belts only) to proper tension.
  4.  
  5. Hold the pump pulley from turning by compressing the drive belt, then tighten the pump pulley bolts.
  6.  
  7. Recheck drive belt tension and adjust it, as necessary.
  8.  

Air Pump Filter Fan Replacement

See Figure 8

Before starting this operation, note the following:

  1. DO NOT allow any filter fragments to enter the air pump intake hole.
  2.  
  3. DO NOT remove the filter fan by inserting a screwdriver between pump and filter fan. Damage to the pump air sealing lip will result.
  4.  
  5. DO NOT remove the metal drive hub from the filter fan.
  6.  
  7. It is seldom possible to remove the filter fan without destroying it. The fan should not be removed unless it is going to be replaced.
  8.  



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Fig. Fig. 8: Servicing the pump filter fan

  1. Remove the drive belt, the pump pulley and spacer.
  2.  
  3. Insert needle nose pliers and pull the filter fan from hub.
  4.  

To install:
  1. Position a new filter fan onto the pump hub.
  2.  
  3. Position the spacer and the pump pulley against the centrifugal filter fan.
  4.  
  5. Install the pump pulley bolts and tighten them evenly. This will compress the centrifugal filter fan into the pump hole. DO NOT drive the filter fan on with a hammer.
  6.  

A slight amount of interference with the housing bore is normal. After a new filter fan has been installed, it may squeal upon initial operation or until OD sealing lip has worn in. This may require a short period of pump operation at various engine speeds.

  1. Install the drive belt and check for proper tension.
  2.  

Check Valve(s)

See Figures 9, 10, 11, 12 and 13

  1. Remove the clamp(s) and disconnect the hose from the valve(s).
  2.  
  3. Unscrew the valve(s) from the air injection pipe(s). Be sure to use a backup wrench to prevent damaging the injection pipe.
  4.  

If difficulty is encountered loosening the valve, use a small amount of penetrating lubricant to help loosen the threads.

  1. To test the valve(s), air should pass in one direction only.
  2.  
  3. Installation is the reverse of removal.
  4.  



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Fig. Fig. 9: Loosen the retaining clamp on the AIR hose



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Fig. Fig. 10: Disconnect the hose from the check valve



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Fig. Fig. 11: If removal is difficult, try a small amount of penetrating lubricant



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Fig. Fig. 12: Loosen the check valve using a backup wrench to protect the AIR pipe



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Fig. Fig. 13: Unthread and remove the check valve from the pipe

Air Control/Diverter Valve

See Figures 14, 15, 16 and 17

  1. Disconnect the negative battery cable.
  2.  
  3. Loosen any retaining clamps, then disconnect the air inlet and outlet hoses from the valve.
  4.  
  5. Disengage the electrical connector and/or the vacuum hose(s) at the valve.
  6.  
  7. Loosen the retaining bolts, then remove the electric air control or diverter valve, as equipped.
  8.  

To install:
  1. Position the valve and secure using the retaining bolts.
  2.  
  3. Engage the vacuum hose(s) and/or electrical connector, as applicable.
  4.  
  5. Make sure the hose clamps are on the hoses, then connect the inlet and outlet hoses to the valve. Secure the hoses using the clamps, but do not overtighten them.
  6.  
  7. Connect the negative battery cable, then verify proper valve operation.
  8.  



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Fig. Fig. 14: Loosen the clamps and disconnect the hoses from the air control/diverter valve



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Fig. Fig. 15: When disconnecting the inlet and outlet hoses, be sure to take note where each is attached



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Fig. Fig. 16: Disconnect any vacuum hoses from the valve



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Fig. Fig. 17: Remove the retaining bolts, then remove the air control/diverter valve from the engine

Mixture Control (Deceleration) Valve
  1. Remove the vacuum hoses from the valve.
  2.  
  3. Remove the deceleration valve-to-engine bracket screws.
  4.  
  5. Remove the deceleration valve.
  6.  
  7. Installation is the reverse of removal.
  8.  

Vacuum Switching Valve (VSV)
  1. Disconnect the negative battery cable, then disengage the electrical wiring connector.
  2.  
  3. Disconnect the hoses from the valve.
  4.  
  5. Remove the vacuum switching valve.
  6.  
  7. Installation is the reverse of removal.
  8.  

 
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