This is on my daily driver V8 305 Caprice. I am testing the egr. I think it is a "negative" backpressure valve, meaning the only force controlling it is vacuum, since the last character in the part number is an "N". Well, when I lift up the valve with ny fingers and put a finger over the vacuum hole on the egr, and release the valve, still holding the vacuum hole closed, SOMETIMES the valve stays up , and then goes back down with a hiss after I release my finger from the vac hole. But SOMETIMES the valve goes staright back down even with finger on the vac hole, ie, sometimes the valve holds pressure, sometimes not.


Is the diaphragm shot? Why would it sometimes hold vac and sometimes not ??



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88 GTA Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

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