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Catalytic converter replacement issues, in need of advice

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Old 06-20-07, 12:46 AM
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deruvian
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Question Catalytic converter replacement issues, in need of advice

Alright, this issue needs a bit of premise/backstory, so please bear with me as I explain away.

My CA registration was due back in May and required a smog certificate (every 2 years), so I had my car smogged. Luckily I'm sorta "in" with a smog shop, so they performed a manual test for me (no pass or fail data is sent to the DMV). This saved me some $$ on the test, and gave me an idea if I would pass without actually failing it first. Turns out I would have failed the real test!

So I have my mechanic take a look at it, and apparently both cats are totally dead (honestly, what did I expect from a 12 year old car and a shady previous owner). After markup on the parts, the front cat is $1100 and the rear cat is $1700. Toss in some labor and you've officially passed the $3k mark. Awesome.

I'm sorry but I can do much better things to my car for $3k. I talked to a buddy of mine that owns a body shop (Chris @ Anything Custom) and can weld well, and he said he'd be happy to chop out the rear cat and replace it with an aftermarket one. I order up a Magnaflow 2.25" cat (#91005), but as it turns out the stock rear cat has an O2 sensor in it so I have to exchange mine for the proper one (2.25", #91035). Not a real big deal, I should have checked into it first. My bad.

The issue is this: Chris discovered that the cat had an O2 sensor in it, and decided to do some research and call some exhaust shop friends of his before giving me the bad news. His concern was that the O2 sensor may not perform as well in the Magnaflow cat. His exhaust shop buddies believe that there is a fair chance that the sensor will read a different temperature in the aftermarket cat, potentially making the car run too rich.

My question to all of you fine people is if you agree with this conjecture, and if any of you are running a Magnaflow/aftermarket cat. If you are, please chime in on some problems you've had (hopefully none).

Also, if anyone is running just the rear cat with the front one chopped out, have you run into any issues? If I can finally get this rear cat replaced and pass the smog test I am certain I'll axe that front cat.

Thanks for your input everyone
Old 06-20-07, 04:06 PM
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deruvian
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Alright, I'm not getting much of a response so here's what I've found (for future people that search like a good little CL member would).

I looked a bit last night and didn't find anything (hey, it was midnight alright!) Today I looked deeper and found some people, both xx300 and xx400 owners, running the 91005 series Magnaflow cats but didn't find anything about anyone having issues after installation. This doesn't mean that there aren't any problems with using them, but it's a good indicator that it's safe to do.

I'll be installing mine soon (after I get the correct one), which should be about a week away. For anyone in CA or other smog-check states interested in ditching one of their cats, I'll also be updating this thread with my smog check stats. If I can pass with just one functional cat, I'll be chopping out the front one or purchasing a new header altogether.
Old 06-20-07, 06:41 PM
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Lexmex
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I have gone through my OEM cat and and am now on my second Magnaflow. Gas down here is the pits. I kept a history of my exhaust on page 3 of my cardomain page below. If you have any questions on cats or smog just fire away, we have big time issues down here in Mexico City.
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