EGR Valve: Description and Operation

Negative Backpressure EGR Valve:

DESCRIPTION
Negative Backpressure Valve
The Exhaust Gas Recirculation (EGR) valve used on this engine is a negative backpressure valve. It varies the amount of exhaust gas flow into the manifold depending on manifold vacuum and variations in exhaust backpressure.

Internal Vacuum Bleed
The diaphragm on this EGR valve has an internal vacuum bleed hole which is held closed by a small spring when there is no exhaust backpressure. The amount of vacuum to the valve is controlled by an Powertrain Control Module (PCM) controlled solenoid valve.

OPERATION
Engine vacuum opens the EGR valve against the pressure of a large spring. When vacuum combines with negative exhaust backpressure, the vacuum bleed hole opens and the EGR valve closes.