EGR System

With engine idling at 900 ± 50 RPM, remove EGR vacuum hose from carburetor and connect to 1.575" Hg (40 mm Hg) vacuum source. A quick check can also be made by sucking on hose with mouth. With vacuum applied, diaphragm valve plunger should retract and permit flow of exhaust gas to intake manifold. Engine should begin to run rough and speed should drop to about 600 RPM (4 cyl. models) or 700-750 RPM (6 cyl. models). If engine speed only drops slightly, check the following; System pipes and hoses may be partially clogged with deposits, stroke of diaphragm valve plunger may be reduced, or diaphragm valve assembly may be leaking exhaust gases.