Bad CAT, and I can't decide what to do... - Fuelly Forums

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Old 02-04-2006, 11:12 PM   #1
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EL has been coming on and off for a year or so now on the TL -- "Bad Catalyst Efficiency". I confirmed today that the catalytic converter is indeed not working as it should (the 02 sensor after the CAT varies in voltage in tandem with the upstream s

OK, so the CEL has been coming on and off for a year or so now on the TL -- "Bad Catalyst Efficiency". I confirmed today that the catalytic converter is indeed not working as it should (the 02 sensor after the CAT varies in voltage in tandem with the upstream sensor, indicating that the converter isn't doing it's job. The downstream sensor should be relatively flat in voltage).

So, here lies the dilemma. The system is forcing the engine to run rich, because it thinks the post-cat emissions contain too little oxygen, but it's just that the CAT's bad. With 126K miles on the odo, and not knowing how long we're keeping the car, I can't decide what to do.

A CAT costs a lot to buy and install, but will reduce emissions and is better for the environment.

If I trick the downstream sensor signal into a flat voltage that's considered richer, the car will rely on the pre-cat sensor and other factors to alter the fuel trim. Right now, it's running rich at +1-1.25 trim, which kills mileage, and I think it's seeing that the post-cat readings aren't right.

We don't have emissions testing, so it won't be tested and require repair, but I guess I know that it's bad. What to do???

RH77
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Old 02-05-2006, 12:18 AM   #2
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I would just buy one of

I would just buy one of those cheap universal cats on ebay and have the a muffler shop install it for you. Should cost about $100 or so.

if all else fails trick the wire to give a constant voltage.
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Old 02-05-2006, 04:52 AM   #3
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cat

I got some really high prices for my Geo exhost from header back from the dealer $1200!!! Blue Book was less than that. So I went to Autozone and got the entire system including cat for about $160

The sensor should be adjustable with either a resistor in series or parallel with it if it is a variable resistor sensor. If it is a thermopile and generates a voltage then it would depend if you need to go higher or lower in voltage to get the better reading. Lower is easy with a resistor across the leads.
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Old 02-05-2006, 08:04 AM   #4
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Quote:I would just buy one

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I would just buy one of those cheap universal cats on ebay and have the a muffler shop install it for you. Should cost about $100 or so.
Do not buy a cat on ebay, they are test pipes, , get one at autozone or something.

Bad cats pollute enough that most sensible states (not MO) have fines from 1k-10k, as well as loss of license, car, and other well deserved stuff.
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Old 02-05-2006, 08:38 AM   #5
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Much Cheaper

For a long time we planned on getting rid of the car this month, but I recently found of that lenders don't like the fact that I have a variable income and I'm technically "self-imployed" (which I just changed to a few months ago). So much for the new Civic right now. Long story short, we'll hold onto the TL and save up for a better down payment (interest rate was rediculous). Hopefully the transmission will hold out (I get a transmission fault CEL every 6-months or so -- basically low-fluid pressure in 3rd gear -- only happens under high-load, low RPM situations). Also, at 90K we put the $1000 timing belt/water pump in, so there's that too.

I thought that it was going to cost a lot more -- I can handle around $100 + installation, really for the sake of the environment. It looks like I'll probably get better mileage, which will help two-fold. I'll probably sell the car outright, so a check-engine light won't help either, but it'll probably be up to 150K miles which won't help either. I should probably run seafoam, plugs and wires, and the the PCV catch system too to get it in tip-top efficiency.

Thanks to all for the advice.

RH77
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Old 02-05-2006, 10:47 AM   #6
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SVOBoy, not all cats on ebay

SVOBoy, not all cats on ebay are test pipes. Making a blanket statement about thousands of different sellers is rather ridiculous.

rh77, after reading a bit on www.bobistheoilguy.com, it sounds like seafoam might not be the best bet for you. Look into a product called auto-rx, which everyone over there loves. It's what I'm going to get to clean my n600 engine.
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Old 02-05-2006, 10:50 AM   #7
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Quote:SVOBoy, not all cats

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SVOBoy, not all cats on ebay are test pipes. Making a blanket statement about thousands of different sellers is rather ridiculous.
I looked every day or two for a month for a cat on ebay, they were all test pipes that were labeled as cats.
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Old 02-05-2006, 12:38 PM   #8
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Still have Seafoam

Quote:
Originally Posted by Matt Timion
SVOBoy, not all cats on ebay are test pipes. Making a blanket statement about thousands of different sellers is rather ridiculous.

rh77, after reading a bit on www.bobistheoilguy.com, it sounds like seafoam might not be the best bet for you. Look into a product called auto-rx, which everyone over there loves. It's what I'm going to get to clean my n600 engine.
I found an OEM replacement for $150, which sounds like a good deal and mates right up with the existing piping, which could decrease install costs. I'm kinda leary about buying a universal.

About the Seafoam -- I still have a bottle or so left from when I bought 2. I went over quickly to Bob's site and found that auto-rx is preferred, but didn't see why. Does Seafoam damage emissions components?

RH77
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