The PAIR system is used only on California cars. It consists of a pulse air valve which has four check valves. The firing of the engine creates a pulsating flow of exhaust gases which are either positive or negative, depending whether the exhaust valve is seated or not.
If the pressure is positive the check valve is forced closed and no exhaust gas will be able to flow past the valve and into the fresh air supply.
If there is negative pressure, a vacuum, in the exhaust system, the check valve will open and allow fresh air to be drawn in and mixed with the exhaust gases. During high engine rpm the check valve will remain closed.
If one or more of the check valves has failed the engine may surge or perform poorly. A short hissing noise may also indicate a defective pulse air valve. Inspect the valve.
When exhaust gases are allowed to pass through the pulse air valve, excessive heat will be transferred to the valve body. This will be indicated by burned off paint or deteriorated rubber hoses. Replace the air valve as necessary.
To inspect the pulse air valve, create a vacuum at the hose end of the valve to 5 kPa (15 in. Hg). The vacuum is permitted to drop to 17 kPa (5 in. Hg) in tow seconds. If the vacuum drops in less than two seconds, replace the valve.
REMOVAL & INSTALLATION
Pulse Air Valve
- Remove the air cleaner and disconnect the rubber hose from the pulse air valve.
- Disconnect the support bracket and remove the attaching bolts.
- Remove the pulse air valve.
- Install the new pulse air valve and tighten attaching bolts to 14-18 Mn (10-13 ft. lbs.).
- Connect the support bracket.
- Connect the rubber hose to the pulse air valve and install the air cleaner.
In some cases the support bracket is not present in the vehicle. If so, simply omit this step.