O2 Problem

00Legacy · Post by **00Legacy** » Wed Jul 22, 2009 7:40 pm

About 2 months after getting both O2 sensors replaced at Pep Boys, (I know, my bad) the check engine light came on. I went to 2 different places to have the codes checked, & both places said that the "Cats" are bad.

Then I went to a friend of a friend to have it checked out, and he told me that the cats were good & the exhaust is all in good condition, but that one of the O2 sensors is not working.

He told me that I can fool the sensor by installing a spark plug "Anti-Fouler" onto the O2 sensor. This will correct the problem.

The car runs great, no problems other than that engine light on. Will this mod fix the problem? I can't afford to buy more O2 sensors.

Which O2 sensor gives the "Bad Cat" code? The front or rear one?

I've already changed the spark plugs & wires for a routine tuneup.

I also read somewhere that you can buy a "Dummy" O2 sensor that works. Is this true?

Thanks for any help on this.....

Post by **Legacy777** » Thu Jul 23, 2009 6:32 pm

Model and year? I'm assuming a 2000 Legacy?

Never heard of a spark plug "anti-fouler". There is some stuff out there that is supposed to trick the ECU, however it's sketchy at best.

The rear O2 sensor is what throws the cat inefficiency code. Which O2 sensor was previously replaced, front or rear?

I'd replace the rear and see how that works.

00Legacy · Post by **00Legacy** » Thu Jul 23, 2009 7:45 pm

It is a 00 Legacy and both front and rear O2s had been replaced. This mechanic said that some after market O2 sensors can turn bad in a short period of time.

As far as using the anti fouler. It is placed in the cat pipe & then the O2 sensor is then screwed into the anti-fouler. This is supposed to send a lower heat temp reading to the computer & fool it.

Again, this is what was told to me that would be a cheap fix.

Post by **Legacy777** » Thu Jul 23, 2009 7:50 pm

What aftermarket O2 sensors did you use?

I would probably recommend using OEM Subaru sensors.

Never heard about the fouler.....I'd guess use at your own risk.

tturnpaw · Post by **tturnpaw** » Thu Jul 23, 2009 8:59 pm

I would suggest an o2 simulator. Replace the rear o2 with one of those, they light should go off and no problems should persist.

As for the "spark plug anti fouler" I think this guy meant an o2 simulator. All it does is fool the ecu into thinking the o2 is there and operating correctly.

As for the quality and concern....Many v8 guys run these for tuning and blocking out unnecessary info, not only that, I do believe that i saw an o2 simulator offered with a chip from cobb tuning.

Never heard any bad things from them. And they are all used on OBDII cars.

Edit: The perrin one is preferred for subarus. Did some searching.

00Legacy · Post by **00Legacy** » Thu Jul 23, 2009 11:12 pm

Here's a how too on the spark plug Non-Fouler or Anti-Fouler I found. http://www.energeticforum.com/renewable ... ulers.html

I found this link after starting this thread.

Is there a certain type/number of this O2 simulator I should get? Or does any type work?

ej22tVermont · Post by **ej22tVermont** » Fri Jul 24, 2009 1:24 am

Stop running the ethanol if you don't have to!! It kills the O2 sensors in any vehicle!! Here in Vermont we still have a handful of non-ethanol filling stations. At our shop we replace and re replace so many O2 sensors due to the stuff!

Post by **Legacy777** » Fri Jul 24, 2009 6:39 pm

ej22tVermont wrote:Stop running the ethanol if you don't have to!! It kills the O2 sensors in any vehicle!! Here in Vermont we still have a handful of non-ethanol filling stations. At our shop we replace and re replace so many O2 sensors due to the stuff!

How does ethanol kill the O2 sensors?

Ethanol has been used as a fuel oxyginate for YEARS (since the 80's)

turboleg · Post by **turboleg** » Fri Jul 24, 2009 9:04 pm

I've never heard much about O2's being killed by ethanol...that being said, I've heard of ethanol cars losing fuel pumps because of improper material construction. I wonder if the sensing elements used in O2 sensors are susceptible to a ethanol combustion chemical attack? I see heat+chemical+stress=bad bad things every day on the job.

I would just replace the O2 sensor. As for buying new sensors, I remember reading a post on here by one of the more experienced Subaru experts. IIRC as long as the threads, the flange above the threads, and the number of wires are all the same the O2 sensor will probably work....your $4 option from a pick-and-pull.

Josh222 · Post by **Josh222** » Sat Jul 25, 2009 1:09 am

Lurker here but have you had a look at the 02 sensor to see if it has been poisoned? Maybe there is a reason your killing them so fast... ie coolant, oil or silicone poisoning.

00Legacy · Post by **00Legacy** » Sat Jul 25, 2009 3:40 pm

This was the 1st time replaced at 125,000 miles. No, I haven't taken it out to look for "poison" What would be the signs?

That's a good idea about going to a pick-u-part and try a used one. So, the one I need will be any "4 Wire O2 sensor"? Would any 4 wire one work from any late model Subaru? Just so long as it is for the cat O2?

thanks for all this help. I would want to just do that Anti-Fouler thing if no one has tried it.

Josh222 · Post by **Josh222** » Sat Jul 25, 2009 9:24 pm

couldn't find the proper chart but this might give you an idea....

00Legacy · Post by **00Legacy** » Sat Jul 25, 2009 11:35 pm

images or link is not showing up!!

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O2 Problem

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