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Old 11-12-2010, 05:12 PM   #1
kevron
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Default 2008 2.5i Legacy with P0420...

So I've got an 08 legacy with the 2.5i automatic with 35k miles and I recently put in a Perrin foam air filter. Within a couple weeks I got a cel P0420 and I thought it was oil coating the MAF so i pulled it out and cleaned it with MAF cleaner and threw her back in. I also removed the filter and tried to absorb as much oil from it as possible. The code stayed off for a while but then when I would come to stops the RPMs would drop WAY down almost to the point of stalling. After about 100 miles or so the cel P0420 came back on but it ran normally again. Wouldn't drop RPMs super low when coming to a stop. So I replaced the front O2 sensor with an OEM and I cleared the code and have driven it about 20 miles without the engine light coming back on but it is dropping the RPMs when I come to a stop again... I don't know how these symptoms are all related but hopefully someone here has had a similar problem. Thanks for all the help!
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Old 11-12-2010, 08:36 PM   #2
tiger2011
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http://forums.nasioc.com/forums/show...hreadid=298963

This might help. Start with post #2
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Old 06-30-2014, 11:02 PM   #3
kevron
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I know this is a dead thread but I just thought I would go ahead and give some follow up since many people probably encounter this same code...

I wasted my money purchasing both new O2 sensors and no success in clearing the code. After extensive research I found an option worth trying... The issue was resolved with a spark plug non-fouler purchased from O'reilly and drilled the end out to 1/2" and used it to pull the post cat O2 sensor out of the exhaust stream. Code went away after about 30-50 miles and never came back. This essentially fooled my ECM into thinking that the cat was performing better than it actually was. No idea why my cat died after 30K miles. Perhaps it does relate to the oil on the MAF from the filter... No idea.
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Old 07-03-2014, 03:32 PM   #4
GEE-OTTO
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Hmm at least youve moved on from that 2.5i I wont go into why that filter and fouler were horrible parts choices or why the cat was actually part of a SOA TB to replace the entire exhaust manifold at no cost to address failing catalyst substrates.
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Old 07-05-2014, 02:11 AM   #5
kevron
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Quote:
Originally Posted by GEE-OTTO View Post
Hmm at least youve moved on from that 2.5i I wont go into why that filter and fouler were horrible parts choices or why the cat was actually part of a SOA TB to replace the entire exhaust manifold at no cost to address failing catalyst substrates.
You are absolutely right about that recall except for the fact that the car had a salvage title and, therefore, no longer worthy of dealership warranty/recall assistance. Bad mouth the fouler all you want but at the end of the day it saved me from shelling out for a cat. I put a good 40k miles on it with that non fouler and never got another CEL, which is awesome since I used CC every day and any CEL will disable the CC... Super annoying.
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Old 07-05-2014, 02:13 AM   #6
kevron
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I also tossed that effin Perrin foam filter and went back to paper. Gas mileage nowadays is not affected by high flow/low flow air filters anyways, just hp.
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