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850 maybe some help?

michael98632

michael98632

New member
Joined
Dec 11, 2009
Location
longview washington
Ok here's the problem. I've recently had some boost problems. Replaced the tcv found two blown intercooler hoses and replaced those. Yet I still can't see more then 2-5psi flat to the floor. Car runs just fine but down on power. Is it possible that I have a plugged cat? I just cannot seem to trace this down
 
plugged cat is very possible. also, check the rubber elbow at the throttle body. I have seen a lot of those leak. reach your finger around it and feel for a hole or tear on the bottom side of it. I have fount this to be a problem a few times now
 
I know that the piece of pipe that links to the throttle body that grows in size had a small hole. I have since patched it after cleaning it up. Gorilla take works wonders.. let me tell you. Held a old hose so well in a ruptured spot that it blew out the other side of the hose.
 
You're sure that your turbo/wastegate are in good working order? Good MPG will also rule out a leak in your intercooler/vacuum hoses. If the O2 sensor detects extra oxygen that hasn't been registered by the MAF, it will start dumping fuel to protect against detonation.

Leaking hoses are also super easy to diagnose, with the engine idling, just spray hoses with carb cleaner or starter fluid and if the idle jumps, it's sucking up starter fluid. Any check engine light or OBDII codes?
 
It did show a high/lean issue when I had a massive boost leak. When I start the car.. I see a "service" light. But no check engine light. It almost seems a leak of some kind. I listened to the car when I revved the engine I heard what sounded like a vacuum leak. Just until the engine settles back into idle. Perfect idle speed, runs so smooth with the exception of low/no boost. I see around 2 at most until gear change then a surge to 5 psi. And as soon as I lift even a small amount it falls to even keel.. right on the zero. Ide like to find out what's going on. But I can't afford shop time.. what ide like to do is find a volvo but locally who can help me lol
 
Well, what I'm saying is, if you're getting 30MPG, it's almost definitely not a boost or vacuum leak.

Your MAF registers the amount of air taken in by the engine and that's the first step to how the computer knows the amount of fuel to deliver. Then your O2 sensor reads the oxygen level in your exhaust fumes and that's how the computer knows that the fuel level is correct.

If your engine is taking on extra oxygen, that is coming in after the MAF, there will not be enough fuel delivered to the cylinders to burn all the oxygen. Then your O2 sensor says, "where is this extra air coming from? Something is wrong!" and starts delivering excess fuel. With boost/vacuum leaks, you can look at your gas gauge and just about watch the needle drop.

Also, with a vacuum leak, you'll usually have no problem getting to the normal boost pressure, it may be a bit slowed, however the level will start to creep lower and lower even at full throttle.

Service light is different from check engine light, it's just reminding you to change your oil (comes on every 3,000~ miles.) You can pull the little rubber plug on the gauge cluster and press the button inside to reset it when you change your oil and it will go away for another 3,000~ miles.

I would still take a look at the wastegate, possibly swap it for a known good one and/or even check for exhaust leaks at the manifold.
 
First clue...replaced the TCV. Did you get the lines on it correctly? Not 'how it came out' but in the actual correct order? If not, and the wastegate is seeing manifold pressure the entire time, you won't get much boost at all, since the actuator is somewhere in the 4-5psi range at most, with boost controlled by the TCV, similar to an EBC.

That said, the wastegate actuators on the 850's are junk, long-known problem. Couldn't get more than 11psi on the R, even with an MBC cranked full tilt. Swapped in a different actuator and first run with the MBC backed off 2 turns saw a spike to over 20psi before I could get out of the throttle. 8 more turns off the MBC and it was finally sitting solid at 13psi without fail, with any pressure I wanted from the MBC easily attained.

Also check your CBV as they are known for cracking. Typically seeing 30mpg you're not likely to have a serious vacuum leak, but there may be something that starts leaking once you roll into boost. I'd bet on a wastegate actuator or incorrect plumbing to/from the TCV.
 
I could have sworn I followed the diagram under the hood as far as routing lines from the tcv to the waste gate and such. Here's what I really don't get. Before changing it I was seeing well over 13psi.. scared me so I thought that the valve was bad. Once I picked the part up and took off home I blew two different intercooler hoses. Since mended them both and replaced the valve. Now I can't see more then a few psi. Its baffling. My big issue is this. I don't fully know the car.. and would much rather have someone who knows what the hell is going on lol
 
If you were seeing more beforehand, and minimal now that tells me they are incorrect.
The middle hose goes to the intake tube.
The top hose goes to the compressor housing.
The bottom hose goes to the wastegate (bottom being the side with the bump on it to locate the TCV in the rubber mount).
 
Sounds like the valve is leaking then. Have you verified that the hoses are indeed hooked up correctly?

If they are, try this.
Unhook all three hoses (since you can refer to this thread for reinstallation, that's not an issue). Put a spare piece of hose on the top one. Key off, blow thru the hose, see if you have airflow out the middle or out the bottom. Next repeat that process with the key in the run position. If you have air from the top to bottom fittings with the key in both positions, you have either a control side issue (wiring) or a dead TCV. If you have air to the middle and nothing to the bottom, you have either a massive boost leak (still may run normal if the leak seals under vacuum, not under boost, but it'll run like crap in boost), or your wastegate actuator is toast.
 
Ok so I did the test you said. Removed the valve and hooked an air line to the top side and had air flow with key on as well as off.. on the factory one. .and the replaced one as well
 
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