P0420 Code and Replacing Cat - Need Help

[Denadai]

Hi all, my GF just bought a 98 Corolla CE and likes it quite a bit. However, it has 145k miles on it, and she took it into the mechanic and got a rude awakening when they asked her for $1200 for a new cat, and also suggested replacing the timing chain. The code received from the ECU was a P0420 - I bought a Haynes manual and also saw from the search button that this indicates "Catalyst system fault" (Haynes manual) and "gas leakage on exhaust system .. or oxygen sensor." She was warned about the cat needing to be replaced when she bought the car, so I think it would likely be that (from what the seller said originally I inferred that it had no cat at all, which wouldn't have restricted flow etc).

So, please forgive my newbness, as I've never done anything on cars that would be considered remotely extensive. I figured the first obvious step would be to remove the cat and see if the light still comes on - however, I don't know what would be the cheapest/easiest way to do this. The Haynes manual says the converter is welded to the center exhaust pipe, and requires "cutting and welding equipment" to remove it. I need details on how to remove it, and what to replace it with. Do I just buy a pipe cutter (or what tool would I use), remove the bolts/disconnect sensors and cut it? Or should it fall out? Also, what would be the cheapest way to replace it? Our town has no emissions standards, so we could run it without a cat, but what would I replace the cat with (ie. how would I connect it to the muffler)? Would I get a junkyard pipe, do I need one at all, if I took it to a muffler shop how much would they charge? We're both college students so the less $ the better. I also read on here after searching that you can find a race cat for about $100 (sure beats 1200), how much would be reasonable to expect a muffler shop to charge for welding it on? I think she'd like to run it without the cat though if possible, would just need to know what to replace it with to keep it running. I've also been told the cat can be cleaned out - is this possible or reasonable? I'm thinking of taking it off and trying to run it first, plus the car does have 145k miles and if this is the original cat then it's probably time for it to go anyways. Again please forgive my naivete

I figured I'd try this first, if it doesn't resolve the code, I'd ask about the O2 sensors. I've also read on here and heard through hearsay that the timing chain should basically never need replacing - the engine was making a small knock before, but isn't anymore, so hopefully it's ok. Is there any way I could tell if the timing chain would need replacing? It seems as if it's ok, just want to be safe, although people here say that it has a non-interference engine which at least wouldn't blow the hell out of it if it were bad.

So basically my questions are, how would I take the cat off, and what would I put in its place to make the car run (ie. connect it to muffler).

[1990geo5speed]

take a hacksaw and saw it off if u have alot of time if not well then get a sawzall and rip through it ..if u cant get that done go to a muffler place have em put in a pipe they should be able to cut it off real fast.and go to autozone and get a new o2 sensor u cant just cut that off and forget it.as far as the timing belt goes i dont know cant help ya there

[REN69]

$1200 for a new cat.. they're trying to rip you off! go to a regular muffler shop and have one installed, probably for under $200.

[Denadai]

Thanks guys, good to know that it shouldn't be so bad. One question: I was going to try to rip off the cat this weekend, and it says in the Haynes manual to disconnect the O2 sensors - Is there a way to know whether it's the O2 sensors or the cat that's putting the check engine light on? (I figured I'd take off the cat and see if the light goes off, but I didn't know if the O2 sensors were in the cat itself or elsewhere, it wasn't clear in the manual).

[mkala2000]

I've been dealing with this issue for several years with my 2003 Corolla. I have almost 200,000 miles now but the P0420 code first appeared at 99,000 miles. I replaced the Cat, came back on, then replaced both O2 sensors, came back on, then replaced the Cat again. It stayed off for awhile, but guess what, came back on. Tried one more O2 sensor, came back on. It varies how long it takes to come back on from 50 to 5000 miles. Now, after being fed up with it, I just erase the code and keep driving it. It's passed two smog checks so far, I just make sure the code is erased before. This code has driven me nuts for four years. I think the computer is faulty, not the parts. I'm going to keep driving it like this and probably keep checking it with smog tests every year.