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Defective O2 sensor

 
Old 03-28-2007, 06:09 AM
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Peter R.
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Default Defective O2 sensor

Out of interest, what would be the symptoms of a failed (or seriously polluted) O2 sensor on an ODBI 993 ? I could imagine everything from severe UNDER fuelling to severe OVER fuelling, including bad idling, engine vibration, dumping raw fuel in the cats, etc.

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Old 03-28-2007, 08:26 PM
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I would like to know too. my CEL lite comes on when sitting at idle and goes out when driving, was told it was my o2 sensor.
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Old 03-28-2007, 08:29 PM
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I can't say exactly for Porsches, but typically for any car, bad O2 sensor results running rich (black smoke)
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Old 03-29-2007, 10:06 AM
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Overfuelling does NOT necessarily mean black smoke. If you SERIOUSLY overfuel a car, it dumps raw fuel through the railpipe which starts evaporating in there, resulting in pure white smoke. This stinks of gasoline, and the residue in the exhaust oval is watery and smells of petrol too. When driven, the car misfires, and when the accelerator is pushed the car stutters.

I know, it's whats been troubling me. I'm taking the O2 sensor out over the weekend.

It is said that white smoke is oil. This is, equally, not necessarily true. Brake fluid can burn white, depending on type. But brake fluid is not really oil.

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Old 03-29-2007, 10:44 AM
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S4 on my back door... I had the exact same problem. Try and read out your OBD codes... (Car off, Hold throttle to floor, turn key to on (not start), keep holding pedal until Check Engine light starts to flash, then read out the code it is telling you - like one short, pause, 7 shorts, pause.) I think an 1-1-2-4 is a bad O2 sensor. Anyway, that is what was happening to me and I replaced it with a Vertex sourced unit. Original Bosch part with factory matching plug end - no splicing. Now that it is replaced, the CEL at idle problem is gone and the throttle response is cleaned up too. For Removal of the old one I had to put a torch on the cat around the O2 sensor to heat that sucker up before busting free.
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Old 04-02-2007, 10:28 AM
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Well, it came out no hassle, but one of the bolts of the undertray support broke off

Anyhoo, the new sensor (correct Bosh part) is on order from the indie parts supplier and is about 130 USD.

Let's hope I can finally move on to one of the finer things in life...DRIVING THE BLOODY THING

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Old 04-02-2007, 01:00 PM
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BS911 thats what my problem is o2. were did pou buy your o2 and do I need 2 of them?
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Old 04-03-2007, 06:38 AM
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Hey, I didn't notice this before. There's a pinhole in the O2 sencor casing (the part that fits inside the exhaust). I haven 't got the new one yet. Is there supposed to be a hole there ? It seems slightly off centered.

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Old 04-03-2007, 06:55 AM
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yes the hole is normal...
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Old 04-03-2007, 10:41 AM
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Hi S4... I got mine from Vertex. www.vertexauto.com They apparently changed their website catalog so finding it may prove tricky. For a 95, you need one, and here is the direct link to hte part...

http://www.vertexauto.com/ShowItem/1...Required).aspx

Costs $99 as of today and I can vouch for its factory part fit. Right cable, right length, right plug that connects directly. No splicing like you would have to do with a generic O2 part.

If you have a later 993, you probably have 4.
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Old 04-03-2007, 10:56 AM
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IF you have 4, there's 2 different part numbers. The cable lengths are different.

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Old 04-04-2007, 02:31 PM
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Well, she's got a new starter, new oil, new filters, a new air mass meter, new sparks, new distributor caps, new rotors, and a new O2 sensor. I also cleaned the ISV.

Started her up, an immediately some white smoke appeared. I almost hit her with da big 'ammer, but the smoking didn't get worse, and disappeared after a minute. Idle was rock solid at slightly under 800 rpm.

Got in, gently took her to the end of the stree, 2nd, doing 20 mph. A couple of lefts and rights, 3rd at 2500 rpm. Gave her some throttle, response was immediate. Accellerated to about 3500 rpm gently. No hesitation, no kiccups. Neutral and coasted, idle immediately solid at slightly under 800. Picked her up again to 3500-4000 and floored it. Response was immediate, sche screamed her head off and went to 95 in third, no hassle, smooth as butter. Came off the throttle, and had a spirited drive to the next village, staying within speed limits.
Parked her, engin running, got out. She purred like a kitten no bumps or hiccups. Let her idle for two minutes, got in and drove home.

The old girl is happy again, and so am I, and all the hassle of the last few months has been worth it.
Next month I'll treat her to a new set of spark pug wires.
This weekend I'll build the OBD box and see what's in the ECU.

My thanks go to all of you, for listening to me whine, and supplying me with endless tips and info. You're a great crew, and I'm happy to be part of it !

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Old 04-04-2007, 02:48 PM
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Nice! Even at my mileage (164,000) it is amazing how the car feels like new after the whole shebang of maintenance. All you need to do now is have a beer and enjoy your accomplishment. Well, don't enjoy the beer WHILE enjoying the accomplishment - you know what I mean.

After all that work, I get a white puff of smoke too.
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Old 04-04-2007, 03:04 PM
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Next up are the RS splitters !

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