I have a '99 9-3 FPT with some boost problems. I have spent some time on diagnosing the system, and I'm quite convinced that boost pressure valve (BPC-valve / APC-valve) is leaking thus not allowing boost to build up normally.
So, where do I find this part? Of course from dealer, but where else? I checked
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and their price is 200USD, which clearly is a rip off.
Do you have any other source for this part? I'm located at US.
Ps. I contacted Saab-dealer back at home on the other side of the pond, and their price for the part is ~70EUR (~80USD). Damn. I guess I have to ask someone to buy it there and ship it to me, unless you know any reasonalble parts suppliers in US?
There are some tests you can do to help determine if this is your problem before you dish out the moolah for a new one. Check out the diagnostic info here. It does not apply directly to your model year car, but the basics are pretty much the same: http://68.18.129.154/turbo_folder/baseboostdia.htm You can also try unplugging the electrical connection to the APC valve. It should run at base boost. Note that level on the gauge. Is that where it runs when the valve is plugged in?
Next unplug the hose labeled W. Be very careful when you drive it. It should run like a bat outta' hell and boost up to the max and then the overpressure safety switch will shut down the ignition.
If the above two steps check out, your turbo is making good pressure and your wastegate is functional. You would have to have some sort of control problem to the APC valve or a bad APC.
OK, thanks. I haven't checked knock sensor (do I have one? where?) nor pressure sensor. I guess I have to try to check those before I buy new BPC-valve. I haven't checked cruise boost limiting switch neither.
I have been warned that this may cause check-engine light to come up. Is that true? I haven't done it for this one reason.
That's exactly what happens, and the reason that made me think it is BPC valve that is shot.
Ok, I guess I have to try to diagnose this pressure transducer. I just hope I knew where the knock sensor is...
Ah, OK. This is the less usual failure mode then. Usually the failure is that you never get full boost, you get base boost only. In your situation you are getting a failure to limit the boost.
What happens if you unplug the APC solenoid? Does it then drop to base boost? If so, you still have a control problem.
If you still get max boost and hit the pressure limit switch the problem is that the wastegate is not being operated. You'll want to see if you can manually move the wastegate. Then try moving it by pressurizing the W hose with a pump of some kind. Also, check that you have pressure coming out of the W port on the APC valve with it unplugged.
Yeah, I get some boost, somedays better some days worse, but never full boost. On one day there was no boost at all (base boost I guess). But when I unplug W-hose, I get all I wanted and more! Of course, I don't dare to drive it like that all the time.
Haven't dared to try that since some people say I get 'check engine' light and I have to visit dealer to clear that. But I guess I have to try it...
OK, I'll try unpluggin APC valve when the problem gets worse again. Now its quite ok. But it seems to come back ...
What comes to the operation of wastegate I made this simple tool: I cut the valve stem from bicycle tube. That fits well into wastegate hose and let's me build up some pressure on wastegate actuator. I pumped air in there with a bicycle pump, which has a pressure gauge and I noticed I need like 0.5bar to wastegate rod start moving. Accuracy of the gauge is poor, but at least I saw that pressure makes wastegate rod move. I believe that part is ok.
I also checked bypass valve, and it does not seem to leak.
BTW; whatever I do with APC valve, touching it always fixes the problem for short period of time (not like days anyway, more like 10-15minutes or so). Then the problem comes back and somedays it is worse, somedays it is better, but unplgging W-hose brings all the boost back. When I play with APC-valve and it starts to work, everything seems ok: smaller boost on first gear (it's manual) and boost goes down a little on high rpms. But then it starts faiing again...
Someone gave me a tip that some CRC or WD-40 may work as a first aid. I did that, and it works now, but that may be just coincidence.
BTW; I haven't made up my mind yet if ambient temperature has something to do with the problem, but I have a feeling it is worse on hot days. Cannot be sure thought. Car also seems to work better when engine is not all hot, but that is also something difficult to tell for sure since I hate to push it hard when engine is cold.
All right, I found your post. I definitely hope fixing this problem does not become quite that expensive for me :)
I had a blocked exhaust four months ago, and symptoms were then just like you describe. However, this time it is little different: when I disconnect a hose that goes from BPC-valve to wastegate solenoid, I get full boost. I addition to that, I'm starting to feel my problem is heat related: when it is hot outside, and engine is hot, I loose boost. Actually, It was in it's worst when it as 34C / 93F outside and I let it idle (AC on) for ten minutes to let interior cool down. When I pulled off the parking lot, I had no boost what so ever. However, boost always comes back when I let it cool down.
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