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Lost O2 sensor? 900 1995

posted by  beefstew on  Mon Apr 16 21:08 CST 2018
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last visit: Wed Jul 16 07:19 CST 2014
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One the way home tonight the exhaust suddenly got really loud on my 1995 945 non-turbo. (Bosch FI w/ EGR). Looking underneath, there's now an open port just forward of the catalytic converter/header-downpipe union. I think I lost the O2 sensor. Anybody else ever have this occur?

Screwing in a new sensor is easy enough, but,

1) I don't feel threads in the open port - it's more like a uniform, round hole. Am I missing a pressed-in threaded fitting? Will I need to tap threads?

2) Where is the O2 sensor wire? I didn't want to lay down in the snow and I couldn't see it from either the top or bottom of the car.

3) It seems really weird that the O2 sensor would just fall out! Is it more likely that I lost a threaded plug for a spare hole in the downpipe?

Thanks for any comments.








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    Lost O2 sensor? 900 1995

    posted by  beefstew on  Mon Apr 16 21:20 CST 2018
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    last visit: Wed Jul 16 07:19 CST 2014
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    Ok, I looked at some parts places - they all show a bolt screwed into the header/downpipe in the location that I see a hole. That seems easy enough, but why is it there? Seems very strange to have an orphan port in the downpipe. Is it for emissions testing? Is the bolt self-tapping? I can't imagine any sealant will hold up to exhaust temperatures...








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      Lost O2 sensor? 900 1995

      posted by  spook on  Tue Apr 17 05:01 CST 2018
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      last visit: Fri Oct 24 08:06 CST 2014
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      Dear beefstew,

      Hope you're well. The Oxygen sensor screws into a port on the forward end of the catalytic convertor. The oxygen sensor is not likely to have come unscrewed and to have fallen-out. The wire from the oxygen sensor is anchored to the underbody. The wire joins a harness on the firewall - near the aluminum cylinder (air-conditioning receiver/drier) - on the passenger side of the engine (US models, non-turbo engine).

      The port on the down-pipe likely is to accommodate exhaust gas recirculation. There likely was a plug in that hole. I think you can tap the hole, and screw in a stainless steel bolt or screw. A high-temp anti-seize (nickel-based, good to 2,500 degrees F) will seal the threads and - should the bolt ever need to be removed - ease bolt/screw removal.

      Hope this helps.

      Yours faithfully,

      Spook







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