EGR Valve: Description and Operation

The EGR control valve is a "negative pressure" vacuum operated valve that compensates for exhaust back pressure. The amount of exhaust gas flow into the intake manifold varies depending on intake manifold vacuum and variations in exhaust back pressure. The valve diaphragm has an internal vacuum bleed hole that is held closed by a small spring when no exhaust back pressure exists. When vacuum is applied via the solenoid vacuum valve, the EGR valve opens against the pressure of the large spring. When intake manifold vacuum combines with negative exhaust back pressure, the vacuum bleed hole opens to close the valve.

EGR Valve:

Exploded View:

Valve Operation: