I have been living with an overboost problem on my '92 9000 for a while now due to financial constraints. The turbo will boost to where it starts touching red on the gauge which will in turn cut out the fuel pump to save the motor...the overall effect is kind of a "bucking" phenomenon. Very annoying, especially on the freeway, and potentially dangerous as power may not be there when needed. A good friend and car wiz (not much experience with Saab, but very well versed in most European makes - he works as a lead tech for a VW dealer) suggested that I replace the APC valve. His suggestion fit in with the reading I have done, so I ordered a new one and slapped it in today. Although the problem is alleviated quite a bit, it ain't gone. WHere would be the next place to look? I want my HP back!!!
Overboost problem
Mar 15, 2005
12 Replies
I had this problem in my 1995 9000 CS (LPT). It turned out to be the wastegate was sticking open. It stuck because water had gotten into it. My mechanic lubricated it, which alleviated the problem for a week or two. Then it came back. He said at that point, the only thing was to replace the turbo, which he did.
Here's hoping that's NOT your problem!
How long is it since you gapped your spark plugs? Running too wide a spark plug gap can cause this problem.
Phuoc
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No, running with incorrectly gapped plugs cannot, under any circumstances, cause overboost followed by fuel cutout.
Have you checked the hose on the wastegate? It's reasonably common for it to rot out or fall off.
Its a hose..!! Check all hoses and replace the worn out ones its a common failure here in sweden ! If you take off the hose to the wastegate you will get full pressure, but then the APC box cuts in. And easy way to get more power is trimming the apc box so that the car can maintain the higher pressure. Consider you "problem" as a health meassure, the protection system is working fine..
I did'nt say it. He said when it "starts touching the red" which is NOT an overboost. Misfires caused by badly gapped plugs can seem like overboost cutout because it creates bucking. It can seem especially bad with worn motor mounts.
Phuoc
A few ideas:
1st, do we know for 100% sure that it really is overboosting and not just that the safety switch is sensing an overboost prematurely? If you have a pressure pump (MightyVac, etc.) you could test the switch to make sure it isn't lying.2nd, if it really is overboosting, can you actuate the wastegate if you hook up to it directly with the same pump? Use the hose that is normally connected to the APC solenoid. How much pressure does it take? Does the pressure hold or does it bleed off?
3rd, triple check the hose-routing to the APC solenoid is correct. If you hose-up the hoses you might be hosed. ;-)-Fred W
"The Malt Hound" wrote in message news: snipped-for-privacy@adelphia.com...
One further point, I had a '92 9000T a while ago and it boosted well into the red area of the boost gauge. You may not have an overboost problem at all.
-Fred W
If the wastegate is stuck open, there wil never be overboost as most of the exhaust gases will bypass the turbo.
-- MH '72 97 '77 96 '78 95 '79 96 '91 900i 16
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Yep, our 2001 9-3 boosts a little into the red on premium gasoline. It's hard to conclude much from that though, without more quantitative measurements.
John
Um, of course. I meant it was stuck closed!
Tom Reingold Noo Joizy
Agreed. My point was that the overboost safety switch should not actuate just at the edge of the red.
-Fred W
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