charm Posted December 31, 2009 Author Share Posted December 31, 2009 Never did follow up with this... Swapping the front O2 sensor didn't do a thing and I am still, 4 months later, battling the 420 code. Since I've replaced the cats and front O2 sensor twice in the last 18 months and 20k miles and the rear O2 sensor once...I'm going to cheat and use the antifouler trick. However, I am still concerned that something else is going on to trigger the code. I suppose it could be that I used aftermarket cats, again, and they're doing it. But seriously? These, unlike the first replacements, are supposed to be good cats. Besides, the mechanic that did this was my cousin's husband, now they're getting divorced so, I can't really go back there anymore. Back to Smart Service where I pay too much but everything always works right. Perhaps if they're actually fixing the thing, I'm not paying too much? Quote Link to comment Share on other sites More sharing options...
idosubaru Posted December 31, 2009 Share Posted December 31, 2009 I wouldn't go to smart service unless they are willing to install the anti-fouler. they're just going to say you need all new subaru parts and to hand over your checkbook and oldest child. find someone to install the anti-fouler and be done with it. it's so dumb how sensitive and unforgiving they made these systems. i've seen folks replace the converters with new Subaru units and still have issues, it's obvious the O2 sensors are very testy. i don't consider it worth my time/money to keep trying to work around a system like that, it's just plain stupid. ignore or anti-fouler all the way. Quote Link to comment Share on other sites More sharing options...
charm Posted December 31, 2009 Author Share Posted December 31, 2009 I'm with you! I'll use my buddy's drill press in the coming days to drill out an anti-fouler and be done with this. Just for fun, I also bought a vacuum gauge. Pretty steady at 21 psi, so I don't think I have a vacuum related issue. Looking forward to not having my CEL on soon. Quote Link to comment Share on other sites More sharing options...
subaru360 Posted December 31, 2009 Share Posted December 31, 2009 Thank god this is a non issue on the newer subarus. 02 and up you can retune the car to delete troublesome codes like 420. On the old ones the correct fix is new converters from subaru. Expensive and not guaranteed to work. I've yet to come across anyone who spends that kind of money on a 10+ year old car. The anti foulers work 90% of the time for me. Is it a perfect solution, no. But I like results. Quote Link to comment Share on other sites More sharing options...
charm Posted January 2, 2010 Author Share Posted January 2, 2010 Well, the CEL came back on with just 1 anti-fouler in place. Just added the second. I'll reset the code in the morning and see what happens. Quote Link to comment Share on other sites More sharing options...
timintc Posted January 2, 2010 Share Posted January 2, 2010 Ive been driving my 2000 legacy wagon for over two years now with the CEL light on and a 420 code and with 170K on the odometer and the car running just fine ive decided to not fight it any longer. The Subie Guys here in my town have tried every fix we could think of, cats o2 sensors exhaust leaks and nothing has worked and since the car runs just fine ive decided to live with it. My only issue would be in selling the car and convincing the next guy to just live with it. Quote Link to comment Share on other sites More sharing options...
subaru360 Posted January 2, 2010 Share Posted January 2, 2010 You need 2 with the first one that goes in the exhaust not drilled for it to work well. Quote Link to comment Share on other sites More sharing options...
charm Posted January 2, 2010 Author Share Posted January 2, 2010 While I don't need to pass smog again until August of 2012, I really like the look of my dash without the light on and, I'd like to know if some other code is being thrown. That said, the car runs fine, this is more an annoyance. Btw, the last set of cats had the CEL off for about a week. The car passed smog and that night the CEL came back on. As you said, I added the second anti-fouler, not drilled, last night. I'll run to the autoparts store to reset the code a little later this morning and see how long it stays off this time. If it comes back on again, I'm giving up until June of 2012. Quote Link to comment Share on other sites More sharing options...
charm Posted March 14, 2010 Author Share Posted March 14, 2010 2 months. I got 2 months of CEL free driving and then the P0420 returned. I'm at a loss here. What the heck am I missing? I've replaced everything in the exhaust chain, I've tried the work arounds, there aren't any exhaust leaks. Is there something on the front side causing something foul, like the cats? What would cause that? I've replaced plugs and plug wires. What do I try next? I'm wary of replacing the cats again. Although next time I do, I'll spend the big bucks and get them from Subaru. If I had done that in the first place, it may have cost me less. Quote Link to comment Share on other sites More sharing options...
hankosolder2 Posted March 14, 2010 Share Posted March 14, 2010 If worst comes to worst, you could install an 02 sensor simulator circuit going to the rear 02 sensor wiring. It will simulate the normal output of an 02 sensor mounted on a car with functioning converters! I don't know if you can find them commercially, but I saw a schematic somewhere online. You'd need a buddy who was somewhat skilled with electronics to assemble it.... Nathan Quote Link to comment Share on other sites More sharing options...
charm Posted June 3, 2011 Author Share Posted June 3, 2011 In case anybody is curious, I think I solved this once and for all...I bought a new Subaru. Actually, no, I didn't do that. I took the car to another exhaust shop, the third that has worked on this project. They told me that they find it very common on the after market cats for all vehicles and at all levels of after market cats, that the welds suck. They almost always have to weld up lots of pin holes on every cat they install where the manufacturer has welded a pipe to the cat. That's what they did for me. Lots and lots of pin holes. $45 later and my CEL has remained off for a week. Another couple months should tell me if this was the culprit. If it was, I think I found me an exhaust shop for life! Quote Link to comment Share on other sites More sharing options...
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