This procedure applies to 1998 and earlier models only. The EGR valve is bolted to the rear cylinder head, at the transaxle end, and the most common problem with this system is usually a stuck or corroded EGR valve. With the engine cold to prevent burns, reach under the EGR valve and push up on the diaphragm; using moderate pressure, you should be able to press the diaphragm up and down within the housing. If the diaphragm doesn't move, or moves only with much effort, replace the EGR valve with a new one. If in doubt about the condition of the valve, compare the free movement of your EGR valve with a new valve.