I recently bought a 96 850 turbo wagon with 177k. Really wellmaintained. It seemed like it ran perfect on the test drive, but after some more driving I have noticed that the power will go up and down when accelerating. It feels like driving into gusty wind. When you go full throttle it isnt noticible at first but, as you approach redline the power seems to taper off and a hissing soundis heard. The car then shifts kind of hard, I assume because of the power loss. I figured there was a boost leak, but I am not really sure where to look. I am new to volvos and turbos, so any advice would be very much appreciated. I did a pressure test involving2 pvc end caps, valve stem, and a bike pump. I am not sure what to look for. When I tested the intercooler and attaching hoses I found the small hole in the bottom of the intercooler. I guess that is not the problem because my wifes S70 has the same thing. Oh yea I forgot to mention the wifes car started this volvo addiction 2 months ago. I found more leaking when testing the intake manifold to exaust, not sure how much it is supposed to leak. The car really runs pretty well, I just want it to run great. Is this a turbo problem, fuel problem, vacume line problem, cat problem, pcv or fuel filter, or what?Are the 850's louder and less powerful than the S70? There is isnt a check engine light on unfortunatly, so I assume a diagnostic tool wont help. Any imput would be greatly appreciated.

 

I would check all the intercooler hoses really good. Also check the hoses to make sure none are collapsing.
You might also want to start replacing all the small vacuum lines to the turbo to be safe.

The hole in the intercooler is for the slight bit of oil that builds up to drain.

That is the only place there should be slight leakage. It should not leak anywhere else in the system.

Also check tune up status mainly the Dist cap,rotor,wires. If they are OEM they will have a date stamped on the wire in white or yellow writting.

 

I agree.Do a tune up first and check/replace any suspicious hoses, then let us know how it is doing. Good luck!

 

Thanks for the help guys, I think thats a great idea. I am going to replace all the vacume hoses right now. The plugs, wires and distributer cap are new so we will start with vacume hoses and go from there, thanks again. I will keep you updated.

 

Well, I bought vacume hoses, but decieded to change the fuel filter first. Wow some nasty crap came out of that. Tons of black chunks and a puddle of pink goo floating in the bottom of the container I drained it into. Car seems more powerful at full throttle, might just be wishful thinking. It still didnt fix the main issue. The car is too hot now to go changing vacume lines, so it will have to wait till tommorrow.

 

Well, changed the vac lines and bingo. No more hissing noise, no more up and down of the power, and wow!!! We go faster now. The transmission still shifts a little harder than I would like under light acceleration, not sure if this is common for the 850s??? My wifes S70 shifts super smooth.

 

You can do a drain and refill of the ATF and see if it helps.

 

DO you have it in SPORT mode? It will shift much harder and stay in gear longer.

 

I have tried both modes it doesnt seem to help in economy. It just does it under light acceleration, when you get on it, it shifts ok. I think I am going to take it in for a transmission service.