ok so recently my 95 850 turbo wagon hasnt been itself . the usual pin you back into the seat isnt even close to what it was and it seemed like a light switch just shut off my power .. i started looking at my boost gauge when accelerting to see if was loosing boost and i deffinetly seem to be . whe i jam the pedal to the floor the boost needle goes as far as the gauge allows and drops to about half way down. PLEASE HELP i want my baby back !
It could also be the Compressor Bypass Valve (CBV). Check IPD's website for some more info, as they have a heavy duty replacement part for this. But, I would check the other items vjaneczko mentioned first, if you haven't already.
I had this problem, low boost, checked CBV and replaced the Boost Control Valve, replaced both items with new ones (IPD kit, Blue Spring) replaced all associated vacuum lines. No Better. I had no other drivability issues (for a week) Decided to check fuel line when I had a hot start problem on a warm day. It seemed like vapor lock- I was losing fuel pressure and getting misfire codes when I would try to start it when the engine was hot. I was stumped, and called a local volvo mechanic. He said that the in tank line that goes from the pump to the housing would come loose because the tube on the housing did not have a barb, and that two hose clamps (super tight) on that hose would keep it on there. I went back and checked in the tank. It was loose, I changed the line, added the second clamp and the boost came back. yay. Aesop's moral, check ALLLL the fuel lines, maybe save a couple of bucks.
The fuel pump hose in my 850 had both a top and bottom clamp. They were both tightened as far as they would go but the top one was really not clamping the tube. As soon as I tried spinning the hose it separated from the upper tube. I have spent four days in an unheated garage tracking down a P0172 engine code and no power/turbo above half throttle and this is what the answer was. My fuel pressure at the fuel rail was 18 psi. Now after replacing the hose clamp it is up around 36 psi. I sure wish I had seen this earlier. I really do appreciate these forums.