I recently started having a problem with having boost at times and others none. I started by going thru replacing vacuum lines which I did find that all the ones that go to the BCS were cracked or totally broken off. Before I replaced all the vacuum lines I was having an over boost issue at times where if I hit the accelerator hard it would over boost and then lose all power for a second or two.

Since I have replaced all those lines I get little to no boost to where the turbo gauge barely goes into the white and not as much power. I have gone thru and checked all the hoses and all are tight and no tears. I also checked for codes and on A2 I got 414, 543, 455, 231, and 443. I went ahead and cleared them and still acts the same. I checked it today after I drove it for 50 miles and no codes have come back.

I also followed a suggestion to test the turbo by removing the wastegate hose that goes to the BCS. After I did that I got boost no problems. I have tried another BCS that I borrowed from friends 850 and still giving me the same issues. This has had me stumped for days tearing everything apart over and over again and rechecking things. I hope someone might know what's going on or have some suggestions.

I was also wondering if in the meantime it's safe to drive the car with the hose off that goes from the wastegate to the BCS till I figure out what the cause is?

 

What lines did you use when you replace them?

 

I used some vacuum line that I got at the auto parts store that was the same inner diameter as what was on there. I also put new clamps on the ends

 

Most likely they sold you fuel line of vac line thats not rated for a turbo car.
Get some silicone lines and re do them. inferior line will collapse during boost and cause problems.

 

I tried to get some at the local auto parts stores around here but none of them carried silicone vacuum lines so I ordered some from IPD which should get here in a few days. I'll update ya as soon as it comes in and I install it.

 

Well I finally got my silicone lines in from IPD. I changed all the lines in the car to the silicone ones. I did see a bit of a difference but it would only give half or less of boost. I had one time to where it gave me full boost but after that I now get no boost at all. I did check my turbo and it's not lose and spins freely with no problems. Any suggestions?

 

So I did some more digging after trying another BCS again from a friends 850 and still no luck but I did find that the plastic hose coming from the PCV to the intake was broken in multiple places. I plan to replace it hopefully this week as long as I can get enough time to do it since I know from my V70 how time consuming it can be.

Would that cause enough of a vacuum leak to give me the issues i'm having?