Chevrolet Citation/Omega/Phoenix/Skylark 1980-1985 Repair Guide

Air Injection Reaction (AIR) System

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OPERATION





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Fig. Fig. 1 AIR management system operation-cold engine



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Fig. Fig. 2 View of the AIR management system schematic-warm engine

The AIR management system, used on 1981-85 vehicles, 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 Management 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 warm-up. When the engine is warm (Closed Loop), the AIR system injects air into the beds of a three-way converter to lower the HC and the CO content in the exhaust.

The AIR system utilizes the following components:

  1. An engine driven AIR pump.
  2.  
  3. AIR management 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 deenergizes the AIR switching valve, thus directing the air between the beds of the catalytic converter. 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 NO x .

If the AIR control valve detects a rapid increase in manifold vacuum (deceleration), certain operating modes (wide open throttle, etc.) or 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 management system check valves and hoses should be checked periodically for any leaks, cracks or deterioration.

REMOVAL & INSTALLATION



Air Pump


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Fig. Fig. 3 Location of the AIR management valve-4-cylinder engine



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Fig. Fig. 4 AIR management valve location-6-cylinder engine

  1. Remove the AIR management valves and/or adapter at the pump.
  2.  
  3. Loosen the air pump adjustment bolt and remove the drive belt.
  4.  
  5. Unscrew the three mounting bolts and then remove the pump pulley.
  6.  
  7. Unscrew the pump mounting bolts and then remove the pump.
  8.  
  9. Installation is the reverse of the removal procedure. Be sure to adjust the drive belt tension after installing it.
  10.  

 
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