Chevrolet Chevette/1000 1976-1988 Repair Guide

Air Injection Reactor



The Air Injection Reactor (AIR) system reduces carbon monoxide and unburned hydrocarbon emissions by injecting air into the exhaust system at the rear of the exhaust valves. The AIR system is used on California cars only. The system consists of an air pump, air injection tubes (one for each cylinder), a vacuum differential valve, an air by-pass valve, a differential vacuum delay and separator valve, a check valve, and the required hoses to connect the components.

The air pump (with an integral filter), compresses and injects the air through the air manifolds into the exhaust system to the rear of the exhaust valves. The additional air brings about further combustion of hydrocarbons and carbon monoxide in the exhaust manifold. The vacuum differential valve stops air injection to prevent backfiring during engine deceleration by activating the air by-pass valve. The vacuum differential valve is triggered by sharp increases in manifold vacuum. On engine deceleration total air pump output is vented to the atmosphere through a muffler in the air by-pass valve. Also in the air by-pass valve is a pressure relief valve which vents excess air from the air pump at high engine speeds. The by-pass valve also vents air through its muffler at times of low intake manifold vacuum (engine acceleration). This low manifold vacuum venting is controlled by the differential vacuum delay and separator valve which blocks this venting during very short periods of 20 seconds or less to prevent possible overheating of the catalytic converter. The check valve prevents exhaust gases from entering the air pump.

When properly installed and maintained, the AIR system will effectively reduce contaminating exhausts. However, if any AIR component or any engine component that operates in conjunction with the AIR system malfunctions, the pollutant level will be increased. Whenever the AIR system seems to be malfunctioning, the engine tune-up should be checked, particularly the PCV system, carburetor, and other systems which directly affect the fuel-air ratio.


Air Pump

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Fig. Fig. 1Exploded view of the air pump mounting

Do not pry on the pump housing or clamp the pump in a vise; the housing is soft and may become distorted.

  1. Disconnect the air output hose at the pump.
  3. Hold the pump pulley from rotating and loosen the pulley bolts. Remove the drive belt and pump pulley.
  5. Remove the air pump mounting bolts and remove the air pump.
  7. Install the air pump by reversing the removal procedure.