I've had a problem which is slowly getting worse. Initially I thought I just had a misfire at high boost, so dropped my boost level abit, and it seemed to be pretty good. Only issue was when it was cold, first 30 seconds if I tried to use alittle bit of boost, which I needed to, due to a big hill outside my house, the bov would open while on boost. This started getting worse and the misfire started happening at lower boost, 17psi. After changing alot of parts on the car, it appears that the bov is opening even when warm on boost, not just leaking, but fully opening.

Since this started, I've replaced the whole fuel system and even fitted a COP and new plugs. Fuel pressure doesn't drop, so its not a fuel or spark issue.

I've swapped my Greddy Type RS bov for an Evo9 metal one, and the issue is just the same. I have an ASI intake pipe, and am hopefully getting my hands on a standard Evo7 one to try as I've read some people have had misfires with aftermarket intake pipes. Any help as to why the bov would open under boost would be very much appreciated.

 

are you sure your not hearing the wastegate open up?

 

How do you know that your BOV is fully open while driving?

 

Definitely bov, and its pretty clear from the sound its opening up more than just a small leak

 

where are you getting your boost vac signal from? Try ruining it on its own line with nothing else T'ed into it, also make sure its on the intake manifold after the the throttle body

 

I've got new hose running direct off the manifold after the TB. This is so weird!!