Negative Backpressure EGR Valve (TBI)

EGR Valve:

EGR System:

DESCRIPTION
The negative backpressure EGR valve has the bleed valve spring below the diaphragm, and the valve is normally closed. The negative backpressure valve varies the amount of exhaust gas flow into the manifold depending on manifold vacuum and variations in exhaust backpressure.
The diaphragm on this valve has an internal air bleed hole which is held closed by a small spring when there is no exhaust backpressure.

OPERATION
Engine vacuum opens the EGR valve against the pressure of a large spring. When manifold vacuum combines with negative exhaust backpressure, the vacuum bleed hole opens and the EGR valve closes.
This valve will open if vacuum is applied with the engine not operating.