1979 Models
- Detach vacuum hose from EGR valve and connect an outside vacuum source, such as hand pump with gauge. Apply about 4 in. Hg and hold this level. Vacuum should not leak down.
- While applying vacuum, watch movement of valve stem. At 4-5 in. Hg, stem should move diaphragm to full up position. If valve does not respond as indicated, it must be replaced.