GM Full Size Vans 1967-1986 Repair Guide

Pulse Air Injection Reactor (PAIR) System



This system consists of four air valves which inject fresh air into the exhaust system in order to further the combustion process of the exhaust gases. The firing of the engine creates a pulsating flow of exhaust gases, which are of either positive or negative pressure. Negative pressure at the pulse air valve will result in air being injected into the exhaust system. Positive pressure will force the check valve closed and no exhaust gases will flow into the fresh air supply.


Regularly inspect the pulse air valves, pipes, grommets and hose for cracks and leaks. Replace the necessary part if any are found. If a check valve fails, exhaust gases will get into the carburetor through the air cleaner and cause the engine to surge and perform poorly.

If exhaust gases pass through a pulse air valve, the paint will be burned off the rocker arm cover plenum as a result of the excessive heat. The rubber grommets and hose will also deteriorate. Failure of the pulse air valve can also be indicated by a hissing sound.


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Exploded view of a common Pulse Air Injection Reactor (PAIR) system

  1. Remove the air cleaner. Disconnect the rubber hose from the plenum connecting pipe.
  3. Disconnect the four check valve fittings at the cylinder head and remove the check valve pipes from the plenum grommets.
  5. Disconnect the check valve from the check valve pipe.
  7. Assemble the replacement check valve to the check valve pipe.
  9. Attach the check valve assembly to the cylinder head as illustrated. Hand tighten the fittings.
  11. Using a 1 in. (25mm) open end wrench as a lever, align the check valve on pipe A with the plenum grommet. Using the palm of your left hand, press the check valve into the grommet. Using a silicone lubricant on the grommet will make thing a little easier. Repeat this procedure for pipe B using your left hand for the tool and your right hand for installing the valve in the grommet.