Date: Thu, 10 Aug 2000 22:26:12 +0200
From: Mathias <af_RGnopsamnt.ser>
Subject: Re: Aero Boost carefully until this is fixed!!! There are a couple of things that usually cause this to happen: 1. Wastegate problem: The wastegate may be stuck or not able to move properly. Verify that the wastegate can move freely. Use a suitable tool and grab the wastegate rod to move it. Preferably this should be done when the turbo has reached operating temp. Be carefull, its HOT. Also check that you have the correct base boost level. While driving, gently put one foot on the brake pedal (just enough to light the brakelight, you will hear a soft "click", you should not do any braking!) and then accelerate hard (while still having your foot on the brake pedal). The boost level should now be steady at 0.4bar which is just before the first red bars on the turbo gauge. If you see that the overboost problem still is present, then please be carefull with this procedure. If you see the needle pas into red when you do this you probably have a problem with the wastegate or the wastegate actuator. If you dont, and the needle is stable just before the first red bars on the turbo gauge, you probably need a new APC valve (some call it a BPC valve, Boost Pressure Control). Now, the same symptoms could also be caused by a faulty APC valve (the one with three hoses, located on the radiator). If there is a problem with the APC valve, the above described test may not be conclusive. We may still see problems caused the APC valve. To eliminate the APC valve from the equation, locate the hoses marked "W" and "C" (there is a label on the hoses or on the valve it self) and connect them. Repeat the procedure above. 2. The APC valve may be "sticky"....The best way to verify if this device is broken or not, is to replace it with a known good valve. You can try to clean the valve by using WD-40 or similar. I would bet my money on a sticky APC valve. These things tend to brake. As you see, these tests are quite simple, anyone can do it. For a mechanic who knows his Saab troubleshooting, this is a 10min job. If they dont know what they are doing, they can probably look for days without finding anything. Good luck! /Mathias 9k Aero '91 Jeff Augenstein wrote: > > I am experiencing a problem with boost on my 94 9000 Aero. There are 2 sets > of symptoms. > > 1) The turbo over-boosts leading to the engine cutting out. This happens > most days under full throttle acceleration. I can prevent this from > happening by modulating boost with the accelerator. The needle on the boost > gauge goes way past the red zone before the engine cuts out. If I modulate > boost with the accelerator I can allow the needle to go a short ways beyond > the red zone before the engine cuts out. > > 2) Other days, full throttle acceleration results in minimal boost with the > needle on the boost gauge only going about halfway into the red zone. > > I reported both of these symptoms to the mechanic at the Saab dealership > when the car was in for its 65K service but they did not fix it. > > I only burn premium from Mobil, otherwise I could blame the gas when I > experience minimal boost. > > Any thoughts on cause and remedy? If I need to take the car in for service > I would like to be educated on the issue before hearing what the mechanic > says. > > Thanks, > Jeff

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