abnormal boost surging - Saab 900 Bulletin Board - Saabnet.com
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abnormal boost surging
Posted by Starch [Email] (more from Starch) on Mon, 20 Dec 2004 17:41:14
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I've been trying to chase down the sourece of an odd boost issue.
At WOT in 3, 4, 5th gear my boost pressure jumps up really fast when I reach a certain engine speed (around 3000-3500rpm). then after a second it cuts back quickly and then continues as it should to incerace/decreace in relation to RPM. I have an LED wired to pin 19 of the APC that flashes when the knock sensor is working so I know that this is not what's happening.
I thought I had fixed it when I noticed the vacuum line to the pressure transducer was bent at a really sharp angle. I replaced this hose and my boost was normal for a day or so then started surging again today. I continued on the theory that I had an under boost leak somewhere but even with the knee bolster removed I've been unable to find anything.
I know I don't have any vacume leaks, and the check valve on the vacuum resevior works and seals.
Any advice?
- dan
89 900t (175hp APC from 91 SPG)
posted by 65.24.230...
Dublin Saab Driver Group
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