Howdy, I noticed someone with a similar problem just yesterday. I buy, sell, and fix cars for fun. I recently bought a 96' outback 2.2 with 135k on it and have restored it into excellent condition. The car runs perfect and mpg is good. Last week my check engine light came on. I have a scan tool (get one if you don't) and it says "catalyst below threshold bank 1". I was about to replace my front cat but remembered this site. I would rather not waste any $$$ on a guess. Could it be a bad O2 sensor instead, maybe the rear cat ?

We have a current thread discussing this topic - look for "catalytic converter question" (it should be fairly high on the current list), and also some references to some other recent threads are listed at the bottom of this thread (scroll to the bottom after you open the question to look at the replies).

 

Good luck and don't break an O2 thread like I did.

Thanks, saw the thread after I posted. Something I left out was that I replaced the air filter and shortly after the cel and code PO420 came on (20 miles). I read the thread about a clogged fuel filter and not enough fuel mixing with air so I took a long shot and replaced the filter. 260 miles so far and no cel. How can this be? Shouldn't another code have come up first, something regarding fuel flow or air fuel mix. I swear, these cars have gremlins in them. This is my third subie and every one of them has had a very strange problem.

We have a current thread discussing this topic - look for "catalytic converter question" (it should be fairly high on the current list), and also some references to some other recent threads are listed at the bottom of this thread (scroll to the bottom after you open the question to look at the replies).

 

Good luck and don't break an O2 thread like I did.

Pretty interesting; hadn't thought of that. Changing your fuel filter at te suggested intervals will also maximize the life of you fuel pump.