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So I think that my Boost Pressure Control valve is not working as it should. I'm getting the overboost fuelcut problem. My research is telling me that the best bet is to just clean it with compressed air. I read a post that said that if you replace it it will probably just need to be cleaned in a year or so anyway.

So I disconnected it last night and blew it out with air. I didn't see any rocks fly out or dust or anything. Put it back on and still same problem. I tested the waste-gate actuator and that is working. Hoses look good etc... I'm thinking I just didn't clean out the BPC well enough.

I shot air into the C and W ports but kinda left the R port alone as it has a much smaller hole and seemed more fragile... I've not been able to find any kind of detailed description of what to do to clean this thing out. Would I be able to us any kind of solvent? Carb cleaner? WD-40? How much air pressure? Which ports?

Any help would be much appreciated. Thanks a million!!!!
Jamie.
 

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Are there any vacuum lines to the boost control??

If so, watch out for diaphragms - use no solvents here. This is why vacuum lines use a trap to prevent gassy fumes...( in Model A Fords ??)
Use a Mity-Mite vacuum pump to test..
In other words ,we need to know exactly how this device works - then it can be effectively serviced..
 

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JamieR said:
So I think that my Boost Pressure Control valve is not working as it should. I'm getting the overboost fuelcut problem. My research is telling me that the best bet is to just clean it with compressed air. I read a post that said that if you replace it it will probably just need to be cleaned in a year or so anyway.
Sounds like you are referring to one of my old posts, where I quoted a mechanic who cleaned my boost pressure control valve with compressed air. He used shop air, but suggested using a can of dry air from an office supply.

I would unplug it first and leave the hoses in place to see if the engine still overboosts. Details below.

Cleaning v. Replacement: Assuming the valve has not failed on your car, the reason for cleaning instead of replacing is simple. On an old car, just like the IAC, once they start getting full of crud a new one will clog up as fast as a cleaned one.

Symptoms: At first the boost just goes down a little bit at a time as the valve gets dirty and operates more slowly. You can hardly tell, most people are at full boost for a few seconds and don't care that much on an older car. I only noticed the difference until it started to stick, had it cleaned, and looked at the boost gauge... :cheesy:

Once the valve starts to stick open between the C and R ports, the engine will overboost, resulting in a fuel cut by the ecu... You definitely notice that when it starts happening. At first it may just be once in a while, then each time on hard accelleration as the engine reaches a higher rpm at wide open throttle.

Connections: The BPC valve has one two-wire electrical connection to the ecu and three pressure ports, one In (C) and two Out (W and R), each with a silicone rubber hose connected to the turbo, waste gate, and the turbo air inlet duct.

C - from turbo Compressor into the BPC valve
W - from BPC valve to Waste gate actuator
R - pressure Reduction port, back to the air intake

To control the boost in the range between base boost and the stock maximum, the the ecu uses the solenoid valve to bleed off some air from "W" (waste gate actuator) to "R" (back to the turbo inlet).

Diagnosing: A leak in one of the BPC hoses, a bad BPC solenoid, or a bad electrical connection can cause the same symptoms as a dirty BPC valve.

With no power applied, the BPC valve should be open from C to W, and closed from C to R.

If you disconnect the BPC solenoid or bypass the BPC valve ("C", compressor directly to "W" waste gate), you should get base boost (middle of the yellow on the turbo gauge), and no fuel cut.

If you get no fuel cut with BPC disconnected, it is the valve.
If you get fuel cuts with the solenoid disconnected, bypass it to make sure.
If you get fuel cuts with the BPC bypassed, there is another problem.

Cleaning: Try compressed air first. I would not use carb cleaner, because ot may not be safe for electrically operated valves. Plain old isopropyl alcohol for a couple bucks at a drug store should do it if a can of compressed air won't, just may take a little longer.

Good luck.

Edit: I should add that although most of this applies both the the NG900 and the 9-3 models, the BPC valve for the 9-3 costs around $50-60, about 1/4 of the cost of the same part on the NG900. At that price replacemant may make more sense than cleaning.
 

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Discussion Starter #4
Thanks PMI for the info! That one should be added to the Boost problems FAQ for sure! :cheesy:
PMI said:
If you get no fuel cut with BPC disconnected, it is the valve.
If you get fuel cuts with the solenoid disconnected, bypass it to make sure.
If you get fuel cuts with the BPC bypassed, there is another problem.
I got fuel cut with the valve disconnected, but when I routed the hose from the turbo compressor to the waist gate I got base boost! Hooray! I'll drive it like that until the replacement part arrives. :D
PMI said:
Edit: I should add that although most of this applies both the the NG900 and the 9-3 models, the BPC valve for the 9-3 costs around $50-60, about 1/4 of the cost of the same part on the NG900. At that price replacemant may make more sense than cleaning.
Unfortunately I already ordered the part from a salvage yard for $45... I would have liked a new one, oh well - this will probably work fine. But too bad for me, my cleaning efforts didn't resolve the problem. You win some, you loose some. ;) I never tried alcohol, but lots of compressed air and WD-40 didn't do anything for it.

Thanks again for the help!
Jamie.
 

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Sounds like the best solution, and you are welcome. I have been meaning to post a better description anyway.

I don't think I would bother cleaning it a second time to save $45. I drove with base boost for weeks while trying to diagnose something else, and the car does not run all that bad. BPC is not really an exact substitute for APC anyway. Note the posts from people who are comparing their T5 and T7 cars to the C900, for example the current "low blow" thread. (I don't include modified cars or chipped engines when I say that).

http://www.saabcentral.com/forums/showthread.php?t=58764
 

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Discussion Starter #6
Update

So I got the part yesterday and installed it last night! Success! After all that I finally realized that my broken valve was open between the W and the R in the disconnected state. The new/used one behaved as described above.

Installed in 30 seconds (I'm really good at this installation now :) ) and I'm running great!!!

Thanks for all the help! This is such a great resource!
Jamie.
 

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i tested today my saab's bpc. i didnt got fuel cut with the electrical wires disconected. This means that the bpc is bad ? It is open from W to C, and close from W to R like PMI said.
I'm trying to figure were my boost is lost.
 

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Anyone know where to get the blue valve coming off PBC?

Sounds like you are referring to one of my old posts, where I quoted a mechanic who cleaned my boost pressure control valve with compressed air. He used shop air, but suggested using a can of dry air from an office supply.

I would unplug it first and leave the hoses in place to see if the engine still overboosts. Details below.

Cleaning v. Replacement: Assuming the valve has not failed on your car, the reason for cleaning instead of replacing is simple. On an old car, just like the IAC, once they start getting full of crud a new one will clog up as fast as a cleaned one.

Symptoms: At first the boost just goes down a little bit at a time as the valve gets dirty and operates more slowly. You can hardly tell, most people are at full boost for a few seconds and don't care that much on an older car. I only noticed the difference until it started to stick, had it cleaned, and looked at the boost gauge... :cheesy:

Once the valve starts to stick open between the C and R ports, the engine will overboost, resulting in a fuel cut by the ecu... You definitely notice that when it starts happening. At first it may just be once in a while, then each time on hard accelleration as the engine reaches a higher rpm at wide open throttle.

Connections: The BPC valve has one two-wire electrical connection to the ecu and three pressure ports, one In (C) and two Out (W and R), each with a silicone rubber hose connected to the turbo, waste gate, and the turbo air inlet duct.

C - from turbo Compressor into the BPC valve
W - from BPC valve to Waste gate actuator
R - pressure Reduction port, back to the air intake

To control the boost in the range between base boost and the stock maximum, the the ecu uses the solenoid valve to bleed off some air from "W" (waste gate actuator) to "R" (back to the turbo inlet).

Diagnosing: A leak in one of the BPC hoses, a bad BPC solenoid, or a bad electrical connection can cause the same symptoms as a dirty BPC valve.

With no power applied, the BPC valve should be open from C to W, and closed from C to R.

If you disconnect the BPC solenoid or bypass the BPC valve ("C", compressor directly to "W" waste gate), you should get base boost (middle of the yellow on the turbo gauge), and no fuel cut.

If you get no fuel cut with BPC disconnected, it is the valve.
If you get fuel cuts with the solenoid disconnected, bypass it to make sure.
If you get fuel cuts with the BPC bypassed, there is another problem.

Cleaning: Try compressed air first. I would not use carb cleaner, because ot may not be safe for electrically operated valves. Plain old isopropyl alcohol for a couple bucks at a drug store should do it if a can of compressed air won't, just may take a little longer.

Good luck.

Edit: I should add that although most of this applies both the the NG900 and the 9-3 models, the BPC valve for the 9-3 costs around $50-60, about 1/4 of the cost of the same part on the NG900. At that price replacemant may make more sense than cleaning.
Well, I found the above quote which seems to have a lot of good info. Basically I've been having issues with my turbo for some time, sometimes the boost works correctly and sometimes it just gets set to "standard boost" in mid-yellow. I cleaned my PBC valve with MAF cleaner and compressed air last wkend and it was working great then yesterday it went back to standard boost, but then on my way home it started working for again?? Not sure what to do. I had tried the "bolt mod" that user Chris discusses on one of the Saab forums, not sure if it's this one, Saabworld or Saabscene. If you google Saab bolt mod you'll find it. Basically just involves taking off the R line (top line) off the PBC and capping it. I tried this a while back and it worked for a long time, but then stopped so I switched it back to normal...it worked for a day or so and now I'm back to standard boost. I'm thinking it may be the blue check valve that is connected to the R line after it splits off. It's on the passenger side at the very front of the car above the low-side A/C port. I have a might vac and need to test it but I think it may be the problem.

I was thinking I should be able to get any check valve that will fit the line, do you agree?

I haven't been able to find one anywhere? I'm debating just replacing all the hose and valves but I can't find a kit anywhere...any ideas? Does anywhere sell a kit? If not should I just get like 10' of silicone heat proof hose? Also if I do that can I just find some check valves that might work? Here's a pic, I would like to replace the valves in this pic...thx!

Also, I believe I used to be getting fuel cut, but I can't say for sure if it's a fuel cut or boost cut....right now seems like a boost cut because it's not quite as noticeable and the boost will stay at mid-yellow. Right before I did the bolt mod it almost seemed more like a fuel cut...any easy way to tell the difference? Thx!

 

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Just to be sure - has anyone succeded in cleaning the apc t5 valve so that it started to work correctly ? I'm having same boost cut under load and I'm wondering if I should make a mod and change to t7 or try to clean it properly.

But I think that the basic question is - does the apc is a thing that gets damaged easily over a time, or it's just becomes dirty... ?
 
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