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inconsistent compression, loud knock, rod bearings? Posted by Michael [Email] (#1365) [Profile/Gallery] (more from Michael) on Mon, 5 May 2008 00:27:13 Members do not see ads below this line. - Help Keep This Site Online - Signup |
2000 9-3 base 57K
After running several diagnostics and the problem becoming more consistent I ran a compression test on my beloved saab today. The readings i got were 90,150,150, and 120 for cylinders 1,2,3, and 4 respectively. I was doing this test with a friend of mine who is quite the engine guru. I then started up the car for him to have him listen to the loud knocking sound my engine is making. He also heard it coming from the area of cylinder 1, and believes that the knock is being caused by a bad rod bearing. He was puzzled by the low compression though because a bent valve should cause a zero compression reading and a bad bearing shouldn't mess with compression numbers. Tomorrow we are going to do a leak test with compressed air to see if there are leaks somewhere that are causing the low numbers. Oh and the cause of this problem I believe is from hitting the rev limiter a few days ago in a moment of immaturity. That is at least when I started to notice it.
The things I have done so far are: checked plugs (good), checked cams and timing chain (appear good), cleaned MAF resistors (more boost :) before problem became this way), completed 60K service recently, changed oil 200 miles ago and every 3K before that with Mobil 1, no codes according to the guy at AutoZone.
Knocking sound frequency increases linearly with revs, independent of tranny, and turbo. Thanks a bunch in advance for any help. I use this board anytime I have problems and it always helps. Look forward to a response.
Mike
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