The air pump system is emissions related and if not working properly will set codes in the ECM (Engine Control Module) and turn on the "Check Engine Light". The Air Pump is part of a system called the Pulsed Secondary Air Injection System (PAIR). The three codes that can be set are; EFI-442 PAIR flow fault, EFI-446 valve leakage, EFI-448 pump flow too high. The EFI-442 is always set with either of the other two codes. When any of these codes are set, fuel trim is disabled.
When you start your car and it is cold, the air pump will start and run for up to two minutes. The Air pump is forcing fresh air into the exhaust to heat up the catalytic converter faster, rather like blowing on a fire. The air pump helps the car to get into emissions specifications faster. The system includes the Air Pump, SAS valve (secondary air system), and the Controller. The Controller is located just under the plastic where the word controller is in the above picture. The Controller receives open and close commands from the Engine Control Module (ECM). When the Controller is opened, vacuum from the intake manifold is applied to the purple vacuum line that routes back to the SAS valve. When the purple line on the SAS valve has vacuum, it will open and allow discharge from the Air Pump to be routed to the exhaust. The Air pump (located just below the battery and forward) is turned on when the Controller is opened. Should the SAS valve stick open because of exhaust gunk building up on the valve, moisture from the exhaust will find its way down to the air pump and eventually fill the Air Pump and Air pump relay with water, causing failure. On a positive note the SAS valve has been changed to open and close better, without sticking open due to engine exhaust. 1996-1997 systems have a relay (for the Air Pump) attached to the air pump frame; in 1998 the relay was moved to the relay box just aft of the air filter box. When undertaking the repair, install a new SAS valve with gasket, Air Pump and relay. When buying the parts make sure you also get the clamps. Sometimes the water in the Air Pump doesn't destroy the relay and it can be used with the new Air Pump.
It doesn't matter which item you replace first, it is nice if the engine is not hot when you are replacing the SAS valve. These pictures are of a non-turbo, however the difference is minimal. To replace the SAS valve you will need a pair of dykes to cut off the clamps on the discharge from the Air Pump hose. The valve is held in place by two 10mm bolts on the under side of the valve. A small stubby 10mm works well to get the bolts out. On a turbo the bolts are very difficult to get out, especially the forward one. Once you have broken the bolts loose, they can normally be unscrewed by hand. I usually take out the bolts and then cut the clamp on the big hose. The purple vacuum line can usually be wiggled off with out having to cut the clamp. The clamps have a special tool to crimp them shut, but if you are careful you can use a pair of dykes to squeeze them tight. Once the valve is removed, install the new green gasket, install the hoses, and then screw in the 10mm bolts. On some of the "Turbos" I have found the discharge hose so hard and brittle that it just falls apart when trying to get it off the SAS valve; if you have this problem you will need to replace the hose as well. You can't cut off the brittle part and then try to work the hose on the valve; it will not fit. The hose can be routed down to the pump fairly easy if you remove the air filter box.
The above picture gives you an idea of what it looks like with the SAS valve removed and ready to install the new gasket and valve.
Sponsored Links: