EGR Valve Opening Test

With engine at normal operating temperature and curb idle speed, quickly open and close throttle. Throttle should open sufficiently to allow engine speed to reach 1500 RPM. A distinct movement should be noticed in EGR control diaphragm. If diaphragm does not move, check for a faulty or leaking vacuum hoses, defective EGR valve diaphragm, or a defective backpressure sensor diaphragm.