Re: APC knock led & boost cut back, never hear it though nm - Saab Performance Bulletin Board - Saabnet.com
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Re: APC knock led & boost cut back, never hear it though nm
Posted by Eric Law [Email] (more from Eric Law) on Thu, 9 May 2002 13:20:47
In Reply to: APC knock led & boost cut back, never hear it though nm, Chad B, Thu, 9 May 2002 12:17:27
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Chad,
First, although it's probably not your problem, .75v is a little low for a good O2 sensor and a rich mixture. I'd expect closer to .9 or even 1.0.
The fact that you don't hear any knocking is a good clue. It's possible the engine is actually not knocking, it's just an APC issue.
The APC system is not the greatest when it comes to distinguishing knocking from other engine noises. If you've got noisy lifters or a loose timing chain, the APC could be fooled into thinking the motor is knocking when it's not. This is particularly likely with a high-mileage engine. One way to test for this would be to unplug the knock sensor and short the pins together, then carefully drive the car and see if the boost stays up.
Another possibility is an actual problem with the APC. Possibly a bad knock sensor - can you get your hands on another to try? A defect in the wiring could cause this, too. Also, if any aftermarket wiring has been installed anywhere near the wiring for the APC system, it can cause interference - I think Saab actually had a service bulletin or two about this. The "disconnect the knock sensor" technique described above may or may not help if it's a wiring problem.
Eric Law
posted by 63.173.23...
Posts in this Thread:
- Lots of gas,too much timing and still knocking at 15psi, Chad B, Thu, 9 May 2002 10:50:46
- carbon?, MS, Fri, 10 May 2002 04:15:00
- Re: Lots of gas,too much timing and still knocking at 15psi, Kevin K , Thu, 9 May 2002 14:07:30
- Re: Lots of gas,too much timing and still knocking at 15psi, Brad, Thu, 9 May 2002 11:57:17
- Few things..., Eric Law, Thu, 9 May 2002 11:14:35
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