Boost problem possible bov issue

adriancork

adriancork

Member
So my legacy hasn’t been running right lately. It’s kind of hesitant just as vacuum becomes boost. Almost juttery. If I floor it in third (4 speed auto) it will take off like a rocket, than it sounds like the car is backfiring from the engine direction. The car shifts to 4th and looses all boost.

anyway I came home from work today and as the car was idling I said I’d Rev it a bit to see if I can hear anything obvious that might give me an idea. If I Rev the car to 2000/2500rpm and let the revs drop to idle there is a pop from the hks ssqv bov. Is this normal? Also I noticed when the bov activates the note it makes changes. Almost like it’s only half blowing.

Any advice appreciated.
 
May be something very simple if theres a funny sound from BOV, quite possible it might have a leak there? Do you have the stock recirc to put on to check that? Or check the gasket and see if it's good and tight.
Some B4s are just known for funny boost issues so following the BOV check, I'd free up a few hours and double check every vacuum hose from the air filter to the intercooler. Some may just be cracked and brittle from age so it may be a chance that its leaking from some hoses too.
If no success there, one of the guys here will surely be able to offer a bit more technical advice on where to check. Best of luck, plenty vacuum hoses with those twins 😃

Also, are you sure your not shifting during transition period from primary to secondary? If you are, the boost can be very hesitant to come on as it has to fully respool before you would get the kick from it.
Think the transition happens somewhere around 5.5 to 6k rpm but could be wrong there....

Hope you get it sorted
 
The bov is the one that came on the car but I’ll take it off and check the gasket. Iv checked all the hoses and they seem all ok. This was by feel and eye. Next step is a test them with a vacuum I’d say. A job for tomorrow.

hopefully it is something simple.
 
As said check all vacuume and boost lines . And standard bov just to rule the other 1 out . When we’re the plugs changed last
 
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I’m not sure when the plugs were last changed, I only have the car since September. Iv a new set here ready to go in. Just to get the time to do it.

I got put in contact with a local mechanic last night that’s stone mad for rallying Subarus. He said he will give it a look over for me during the week so hopefully he can diagnose the issue for me. I’ll update ye during the week.
 
Quick update.
I found a small blow from one of the manifolds at the gasket. Ordered what gaskets I could get from Subaru and waiting for the last one to arrive from Germany. Coudnt get over how bad one of the gaskets were. Completely rusted out. Fingers crossed this is the issue. It was a tiny blow but only seen with the car running and feeling around the flanges.
 
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