Closing Test
- With engine at normal operating temperature, manually depress EGR valve diaphragm. This should cause an immediate drop in engine speed.
- If not, passage between EGR valve and manifold may be plugged. If engine idles rough and is not affected by depressing diaphragm, fault is in hoses or EGR valve.
- If engine idles properly but there is no change in RPM when valve is depressed, exhaust gases are not reaching the combustion chamber. There is probably a plugged passage between the EGR valve and the intake manifold.