The big 420a Mystery! Please Help!!!

[gallacmic]

Alright so I thought I would post an update about the BOV issues I have been having as I just made a discovery today. I decided to buy one of those Harbor freight brake bleeder vacuum pump kits that has a gauge on the vacuum gun. I first connected the gun to the hose that feeds the BOV its boost and vacuum pressure and started up the engine. The gauge read 15hg at idle. I also know that the exact opposite of 1hg is .5 psi. So you want a spring that has half the pressure rating of whatever the hg is on the vacuum gauge. So in my case 15hg means I need a 7.5 psi spring in the BOV. So next I disconnected the gun and hooked it to the BOV to do a vacuum test on it to see when the spring would open up. NO VACUUM AT ALL!!! The BOV will not even hold 1hg of vacuum!! GO FIGURE IT PASSES THE BOOST LEAK TEST!!! So that was the mystery! I need to seal it for both boost and vacuum in order for the engine to do its job to open the damn thing. I never would have guessed that the BOV is not getting any vacuum above the diaphragm. But anyways now I know what I need to do I hope this helped point someone in the right direction if they were having similar issues. Also thanks again to all the nice people who responded to this post to help me out!

[SilvrEclipse]

My bov also will not hold vaccum in a test like that, it has a slow leak but this doesnt effect it since the motor is sucking so much air that it over comes this small leak. You are looking into this too much, with the car idling look at the bov and see if its opening, when you rev the motor the valve should close and open as the motor pulls high vac. If it does not open then you need to lower the spring