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Pre Cat O2 sensor going bad. Yesterday for the first time it triggered a CEL going 80mph at WOT.

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Old 11-20-2008, 05:05 AM
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Default Pre Cat O2 sensor going bad. Yesterday for the first time it triggered a CEL going 80mph at WOT.
Its an intermittent issue. I've noticed it throwing codes for a while which I always cleared but never a CEL.

Now, should I wait until it dies completely or replace it right now? What can I expect from a bad pre cat o2 other than worse gas milage. Currently I still make 320 miles/tank in the city. Will the car be running lean or rich?
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Old 11-20-2008, 05:21 AM
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Replace it now and be done with it.
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Old 11-20-2008, 05:39 AM
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but its espensive!
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Old 11-20-2008, 05:41 AM
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as expensive as a new engine?
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Old 11-20-2008, 05:55 AM
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it's not gonna blow your engine, just use a little more fuel
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Old 11-20-2008, 06:06 AM
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if it goes lean? How do you predict what a faulty O2 sensor will do?
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Old 11-20-2008, 07:26 AM
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$150 isn't THAT much considering how stupid easy it is to replace.
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Old 11-20-2008, 07:58 AM
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Default Pre Cat O2 sensor going bad
same thing happened with mine it Vag said bank 1 sensor 1 slow to warm. It was an easy replacement. I ordered from an online vendor and it was a little cheaper than 150.
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Old 11-20-2008, 08:16 AM
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Default 2nd... My car went lean when the primary O2 went. Replaced it ASIC, but my AF didn't
center where it was supposed to until I replaced the MAF and yanked out the SAIS.
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Old 11-20-2008, 10:44 AM
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That is because it is a critical component...
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