GM Caprice 1990-1993 Repair Guide

Air Injection Reaction (A.I.R.) System

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See Figures 1 through 6



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Fig. Fig. 1: Air Injection Reaction system with cold engine - except 1992-93 5.0L & 5.7L engine



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Fig. Fig. 2: Air Injection Reaction system with warm engine - except 1992-93 5.0L & 5.7L engine



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Fig. Fig. 3: AIR pump mounting and components - 5.0L (VIN Y) engine



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Fig. Fig. 4: AIR pump mounting and components - except 5.0L (VIN Y) engine



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Fig. Fig. 5: Pressure operated Electric Divert/Electric Switching (PEDES) Valve - except 5.0L (VIN Y) engine



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Fig. Fig. 6: Electric Diverter Valve - except 5.0L (VIN Y) engine

OPERATION



The AIR management system, is used to provide additional oxygen to continue the combustion process after the exhaust gases leave the combustion chamber. Air is injected into either the exhaust port(s), the exhaust manifold(s) or the catalytic converter by an engine driven air pump. The system is in operation at all times and will bypass air only momentarily during deceleration and at high speeds. The bypass function is performed by the Air Control Valve, while the check valve protects the air pump by preventing any backflow of exhaust gases.

The AIR system helps reduce HC and CO content in the exhaust gases by injecting air into the exhaust ports during cold engine operation. This air injection also helps the catalytic converter to reach the proper temperature quicker during warmup. When the engine is warm (Closed Loop), the AIR system injects air into the beds of a three-way converter (except 1992-93 5.0L & 5.7L engines) to lower the HC and the CO content in the exhaust.

The Air Injection Reduction system utilizes the following components:

  1. An engine driven AIR pump.
  2.  
  3. AIR Control valves (Air Control, Air Switching).
  4.  
  5. Air flow and control hoses.
  6.  
  7. Check valves.
  8.  
  9. A dual-bed, three-way catalytic converter.
  10.  

The belt driven, vane-type air pump is located at the front of the engine and supplies clean air to the AIR system for purposes already stated. When the engine is cold, the Electronic Control Module (ECM) energizes an AIR control solenoid. This allows air to flow to the AIR switching valve. The AIR switching valve is then energized to direct air to the exhaust ports.

When the engine is warm, the ECM de-energizes the AIR switching valve, thus directing the air between the beds of the catalytic converter (except 1992-93 5.0L & 5.7L engines). This provides additional oxygen for the oxidizing catalyst in the second bed to decrease HC and CO, while at the same time keeping oxygen levels low in the first bed, enabling the reducing catalyst to effectively decrease the levels of NOx.

If the AIR control valve detects a rapid increase in manifold vacuum (deceleration), certain operating modes (wide open throttle, etc.) or if the ECM self-diagnostic system detects any problem in the system, air is diverted to the air cleaner or directly into the atmosphere.

The primary purpose of the ECM's divert mode is to prevent backfiring. Throttle closure at the beginning of deceleration will temporarily create air/fuel mixtures which are too rich to burn completely. These mixtures become burnable when they reach the exhaust if combined with the injection air. The next firing of the engine will ignite this mixture causing an exhaust backfire. Momentary diverting of the injection air from the exhaust prevents this.

The AIR system check valves and hoses should be checked periodically for any leaks, cracks or deterioration.

TESTING



Air Pump
  1. Check the drive belt tension.
  2.  
  3. Increase the engine speed and observe an increase in air flow. If air flow does not increase, replace the air pump.
  4.  

Control Valve
  1. Remove the hoses. Blow through the valve (toward the cylinder head).
  2.  
  3. Then, blow air through the other side of the valve in the direction of the pump. Air should only flow in one direction, toward the cylinder head. If not, replace the control valve.
  4.  

REMOVAL & INSTALLATION



Air Pump
  1. Remove the AIR control valves and/or adapter at the pump.
  2.  
  3. On 1990-91 Caprice, loosen the air pump adjustment bolt and remove the drive belt. On 1992-93 Caprice, hold the pump pulley from turning and loosen the pulley bolts. Lift the belt drive tensioner to the raised position remove the pump and pulley assembly.
  4.  
  5. Unscrew the pump mounting bolts and then remove the pump pulley.
  6.  
  7. Unscrew the pump mounting bolts and then remove the pump.
  8.  
  9. To install, position the pump into place and secure it with the mounting bolts.
  10.  
  11. Install the pump pulley.
  12.  
  13. Install the air pump drive belt and adjust pump belt with the pump adjustment bolt, as required.
  14.  
  15. Install the AIR control valves and/or adapter.
  16.  

Check Valve
  1. Release the clamp and disconnect the air hoses from the valve.
  2.  
  3. Unscrew the check valve from the air injection pipe using a back-up wrench.
  4.  
  5. Installation is in the reverse order of removal.
  6.  

Air Control Valve
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner.
  4.  
  5. Tag and disconnect the vacuum hose from the valve.
  6.  
  7. Tag and disconnect the air outlet hoses from the valve.
  8.  
  9. Bend back the lock tabs and then remove the bolts holding the elbow to the valve.
  10.  
  11. Tag and disconnect any electrical connections at the valve and then remove the valve from the elbow.
  12.  
  13. To install, position the valve into the elbow.
  14.  
  15. Connect any electrical connections at the valve.
  16.  
  17. Install the bolts holding the elbow to the valve and bend the lock tabs.
  18.  
  19. Connect the air outlet hoses to the valve.
  20.  
  21. Connect the vacuum hose to the valve.
  22.  
  23. Install the air cleaner.
  24.  
  25. Connect the negative battery cable.
  26.  

 
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