Valve Opening Test
- With engine at normal operating temperature and at curb idle, rapidly open and close throttle (open throttle sufficiently to obtain at least 1500 RPM). A definite movement should be noticed in the EGR diaphragm.
- If diaphragm does not move, probable causes are: faulty vacuum signal to EGR; defective EGR diaphragm or defective back-pressure sensor diaphragm (if equipped); or leaks in vacuum lines or connections.