So my check engine light came on a few days ago(2005 2.5RS w/just under 80k), i reset the ECU to have everything reprogrammed, i had recently replaced the headers and catback. the car ran like complete crap after that. The car is down on power, and will die when the revs drop. The check engine light came on after that, and the car seemed to run okay when the light was on. So i went to checker and used their scan tool and pulled the code, turns out to be a P0420, Catalyst system efficiency below threshold(bank one). So i cleared the code, and now the car runs like crap again, and the CEL has yet to come back on. Anyone have any ideas as to what that would be? Would an O2 sensor throw everything enough to be causing all these problems?
p0420 is not an o2 sensor code its saying that the cat is bad. that the 2 02sensor are reading about the same( one 02 sensor is before the cat one is after the cat.) they should read different. are u sure u got everything pluged back in, no leaks from when u did the headers or the catback??? it almost sound like u have a vaccum leak some where( cause u said the car dies when revs drop/cars running like crap)
What kind of intake does it have? Running like crap after the reset would mean something is out of wack (no the cats wont cause runability problems) and it runs better after a while because it learns your mods.
its the stock intake, there is an exhaust leak from the headers, but its pretty small, and the headers have been on for almost 2 months without any problems. The car just continued to die until the check engine light came back on. then it seems to run better. If i would hold the rpm's at about 1500, they would constantly go up and down. Would that check engine light put the car back into a sort of limp mode with just factory ratios on everything?
yes the check eng light puts the car into a limp mode. not on a subi but on my old bonneville i had a 1/4in vac. line brake and every time the rpm will drop/come to a stop the car would die on me. it took me about 2days to fine the broken line. it broke at a Tfitting and at first glanced it did not look broken i would 2X check that eveything is hooked up right. How did you reset the ECU
sorry, intense weekend. From talking with a few people it seems that the error code i am getting is not an o2 sensor. If it were, it would post a sensor 1 or sensor 2 error, but in fact it is the cat that is bad. If i were to just remove the cat, would i be able to put a fake sensor in the downstream sensor, or would that mess up the readings? its alot cheaper way to go then spend $400 on a new cat.
Speaking from the perspective of a 2000 RS, the 'bad cat' should not affect the performance of the car like that. I haven't had a cat on the RS in 4-5 yrs and the only side effect is the ever glowing CEL. Maybe they changed something between 2000 & 2005, but if not, sounds like you are tracking down the wrong issue.
You could put a spark plug arrestor on the rear o2 sensor which should bring it up and out of the exhaust flow enough to stop it from throwing that code, thats how the previous owner of my car got around that after gutting the stock cat. It is usually referred to as a mechanical fix when people put in an aftermarket downpipe. If your ECU is rom raider compatible, maybe someone could flash it to defeat the code as well (assuming it works like the turbo models).
i am assuming that this isnt a vacuum leak, or anything of that nature, because as soon as the check engine light is triggered, the car seems to run almost fine, if it were a leak issue, then the problem would continue, leaving me to think that it has to be something with the fuel delivery, being as its a catalytic converter efficiency error. Would wrong readings from an o2 sensor be enough to make the car run too lean/rich enough to let it die? in any case, starting with an o2 arrestor seems to be the cheapest option by far, so i will try that, and if that doesn't fix it, go from there. I called both NAPA and O'Reillys and neither of them carry the o2 arrestors. Anyone know where I can pick one up?
part: Help! Spark Plug Non-Fouler part # 42002 pepboys you will need to drill it, maybe. http://sl-i.net/FORUM/viewtopic.php?f=39&t=14675 napa part #730-2443 non fouler
