I wanted to make sure that the egr valve on my 96 Z28 is working properly. I started the car, and reached behind and manually moved the the diaphragm moved up, which caused the engine to run rough. So I'm ok there.

So I disconnected the hose from the control solenoid, and installed a hose connected to my manual vacuum pump directly to the egr valve. I drew vacuum, and the diaphragm moved up, but came back, not holding any vacuum.

According to shoebox's website, the egr should hold vacuum. But I'm thinking the vacuum needs to bleed off because the ecm needs to control the egr valve to open and close when need be.....I guess.

Can someone advise? Thanks!!!

 

The valve should hold vacuum for at least 20 seconds. Bleed control passages in the valve come into play when the engine is running and there is exhaust back pressure.