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Old 09-04-2013, 12:38 AM   #1
VettezukiVettezuki is offline
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Default Bad O2/Cat Relationship

I have a situation on the Aveo from hell, where I know the O2 sensors are bad because the computer will throw a code immediately after clearing it. Here's the question:

If know the O2 sensors are bad, but don'tkow if the cat is bad, what's the best way to proceed? My understanding is that a bad cat can wreck at least the downstream O2 sensor, and if the ECU gets bad data, it can also lead to a condition where both O2 sensors get toasted.

All I know to do is put in the new O2 sensors, but I'm not going to be happy if they get chewed up right away. How can I avoid that?
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Old 09-04-2013, 08:49 AM   #2
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Before you change the O2 sensors out, you can run the engine for awhile and then use a temp gun to see what the temps are right before and after the cat. If its hotter before the cat, it's bad.
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Old 09-04-2013, 09:01 AM   #3
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Check the part numbers on the O2 sensors. If they are the same than a bad cat will not damage the downstream O2 sensor. O2 sensors are $50 to 100 I would just replace it and see what happens.
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Old 09-04-2013, 09:23 AM   #4
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Quote:
Originally Posted by BADDASSC6 View Post
Check the part numbers on the O2 sensors. If they are the same than a bad cat will not damage the downstream O2 sensor. O2 sensors are $50 to 100 I would just replace it and see what happens.
They're different and quite a bit different in price. Don't know if that's just the length of the pigtail, or something else, but they ain't the same part.
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Old 09-04-2013, 10:05 AM   #5
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Like Damian said, check the cats with a temp gun. Run the engine at around 3000 rpms for a couple minutes and then check the temp before and after the cat. The temp out of the cat should be about 300 degrees hotter if the cat is working properly.
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Old 09-04-2013, 02:37 PM   #6
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Thanks for the cat check protocol. I shudder at having to replace that as the cheapest cats are fuck all expensive.
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Old 09-04-2013, 02:44 PM   #7
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That's where I'm at on the Cobra. I think I'm going to add front cats to the current H pipe which are about $130 each. A complete four cat H pipe is about $550. I might be able to get a stock one that's missing a front cat but I don't know yet. I haven't tested my cats yet but my current H pipe only has 2 cats.
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Old 09-04-2013, 02:59 PM   #8
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The one (1) cat on the Protege was like $750. I think they are like $650 on the LS1 AIR. It's not total BS though, OEM cats have a lot more catalyst and platinum in them than aftermarket, which borderline isn't even legal anymore. The law is pretty fuzzy to me. Paul would know, but in the Aveo case, basically a dealer item.
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Old 09-04-2013, 03:27 PM   #9
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Quote:
Originally Posted by 94cobra69ss396 View Post
That's where I'm at on the Cobra. I think I'm going to add front cats to the current H pipe which are about $130 each. A complete four cat H pipe is about $550. I might be able to get a stock one that's missing a front cat but I don't know yet. I haven't tested my cats yet but my current H pipe only has 2 cats.
I never used the cats you gave me. You're welcome to them back.
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Old 09-04-2013, 04:13 PM   #10
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Give me the part numbers for the O2 sensors and I will check to see if we manufacture them. If we do I might be able to get you a good price on them.
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