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11-18-2012, 02:47 PM | #1 |
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o2 sensor replacement with catalytic convertor?
Replacing exhaust on my 2005 Subaru Impreza RS with a Cat back system and a OEM replacement catalytic convertor (Eastern). The car has 60,000 miles on it and the mechanic who did the inspection said it had a bad cat as well as needs new water pump ,etc. He is a good and honest mechanic I know for awhile.
My question is, when I replace cat should I just go ahead and replace upstream and downstream O2 sensors at the same time since I will be replacing everything? Or, is this a waste of money and I should just keep using the same sensors. Be interested to here others opinions about this. Most postings I read on here are when people get the CEL codes and then they have to fix it. Just thought it maybe best to do preventative maintenance. Also, I will be rallying car a bit and need it reliable and running efficiently.
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11-18-2012, 03:48 PM | #2 |
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Personally I wouldn't bother to get new sensors unless you can get a deal on them. It doesn't really save you a bunch on labor, if you need to replace one later. And atleast on my car the cheapest I could get both for was over $200, And that was on amazon, non-universal type.
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11-19-2012, 02:47 PM | #3 |
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I like to take them out and burn the carbon off every once in a blue moon. Just grab a propane torch, heat the tip up till it's close to glowing, and repeat all over the sensor tip. The carbon comes right off and they seem to respond quicker again.
Eventually though it will be a dead sensor and require replacement. I'd also try seafoaming the car to see if the cat can be "cleaned" that way. Unless the catalyst itself is majorly damaged or partially melted you can usually get them clean enough to work again. |
11-19-2012, 03:05 PM | #4 |
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OP, just replace the cat and forget about the sensor, if it's not giving you issues then why spend the money. Its a quick 2 min job when the time comes anyway.
Neat trick, I'll have to try that. |
11-19-2012, 03:47 PM | #5 |
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I suppose if you get them too hot for too long you will damage them. But so far so good here. I had a bad pre O2 exhaust leak and both sensors were extremely sooty. Burning them clean the car ran much better no changes (did it a day ago.) Yesterday night I went around doing logging and scaled my maf, even better than before.
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11-19-2012, 03:52 PM | #6 |
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That's exactly what I needed to hear
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11-19-2012, 09:25 PM | #7 |
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Great ideas thanks - I decided to wait on O2's as suggested. May even wait on cats for now. The mechanic says a metal shaking sound when I start the car is the cat. it goes away quickly - I thought maybe it is the heatshield or something - so I will wait until I see a drop in performance from a clogged cat or something. Any other signs to verify the cats are bad?
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11-20-2012, 02:02 AM | #8 |
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DTC P0420 and a check engine light accompany a bad kitty, but can still be downstream O2 sensor. if you are not concerened with emissions and just want to pass you can always use a "spark plug anti fouler" drilled out to use as a spacer on the O2 sensor, rather than replacement, if the converter is bad. Costs $5...
And as far as reliability and efficiency go, a bad kitty (or downstream O2 sensor for that matter) only effect would be increased HC, CO, and NOx emissions. It would have no impact otherwise on the car. Does your mechanic have any other reasons for thinking the cat is bad? heatshields make all kinds of rattling noises and are easy to fix... I would never even think about replacing a convertor as "preventative maintenance". If the water pump is bad, go ahead and do a timing belt and a tensioner at the same time. It should only cost you the parts no extra labor. Last edited by ProdriveDreams; 11-20-2012 at 02:10 AM. |
11-20-2012, 09:03 AM | #9 |
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If that cat is clogged up or partially melted, it can cause even more exhaust obstruction and raise EGT's to exhaust valve greying/cooking levels. The heat shielding on them is easily removed with a cut of wheel and swearing.
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11-20-2012, 11:36 AM | #10 | |
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11-20-2012, 11:52 AM | #11 |
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When I read through OP it doesn't sound like a bad cat at all. So, you don't have a CEL just a rattle while cold? That's like the official noise of Subaru heat shielding.
My advice. Go to dealer if you are worried. If your cat is bad it should still be under the 80,000 mile emissions warranty and be free. As for water pump why do you need a new one of those? I'm guessing this mechanic not very knowledgeable on Subaru? |
11-20-2012, 12:05 PM | #12 | |
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Quote:
Where the heat shield is rattling against itself, grab a big worm drive pipe clamp from the hardware store and slip over that section, then tighten down like crazy. When I worked at a Subaru dealer that was what we did to alleviate customer complaints of heat shield rattles. Fast, easy, and leaves the shield intact. And its swear free. which depending on your disposition may not be a feature. also a cat clogged that bad would not be symptom free... you would know something was wrong. |
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11-20-2012, 12:53 PM | #13 |
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^^ good call.
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11-22-2012, 12:04 AM | #14 | |
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11-22-2012, 12:07 AM | #15 | |
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