2001 Monte Carlo SS 3.8L

Well I'm thinking I might be in need of ANOTHER catalytic converter. I was talking with my nephew about this damn P0420 code which keeps plaguing me. I bought some stupid Evan Fischer (universal cat) off Ebay back in July of '13. I'm gonna have some diagnostics done to pinpoint whether its the cat or possibly the o2 sensor but my nephew is leaning towards the aftermarket cat as being bad.

So for my question? What do I wanna put on this so I don't run into the same problem again? Are Magnaflows good and do they function as an OEM? I see they are listed as "OEM grade". Is there something else I should be looking at manufacturer wise? I don't really wanna spend an arm and a leg as I already have $170 wrapped up in this universal crappy one that's on the car right now but I'm afraid I'm looking at getting a new one.

Thanks.

 

Did you hook up the rear 02 sensor after installing the new cat?

When you run your car does the cat heat up and turn glowing red? symptom of a clogged cat

How is the car running other than the code?

With our cars if one of the 02 sensors is bad it will throw the code,3800 performance sells an eliminator for the rear sensor if you want to go with an aftermarket downpipe
Rear 02 Emulator
Rear O2 Emulator: 3800 Performance

and then you could run a downpipe similar to this
ZZPerformance - ZZP Downpipes #ZZ-GPDP

with or without a catalytic converter. They are both fairly cheap alternatives that may work for you.

 

Yes I actually replaced both o2 sensors with AC Delco sensors after installing the universal cat and the car seems to run OK for the most part. I haven't checked if its glowing red after running it or not. I read where you can do that so I'll take a look at it after I run it next time.

My nephew was telling me about the specs the front and rear o2 sensors should read so he's gonna read 'em I guess with a multimeter? He says he's pretty confident he can pinpoint it within about 30 minutes time as to whether its just an o2 sensor OR if the universal cat has went bad. This damn catalytic converter is only about 6-7 months old.

Thanks for the links I'll check them out.

 

So in doing some reading on here am I right in my assumption that the aftermarket cat may not be bad? It looks like I'm reading where these cars emissions are so "tight" that the code gets thrown and it may not be a bad cat or o2 sensor at all? I'm assuming that is why you asked if its glowing red?

 

It sounds like your nephew is on the right track to resolving your problem. I would see what he comes up with then plan a line of attack from there.

 

I run a Magnaflow hi-performance cat with front O2 sensor delete and it is great...

 

Yeah he's pretty handy with a wrench he was already telling me what the front should read and what the back should read and if they read the same that its a problem or if the back is "stuck" and so forth.

So you mean its been deleted from the PCM? If it comes down to the cat and o2 sensors being good still I'm thinking I'll have the PCM tuned (if that is what you're talking about by the "O2 sensor delete") and have that P0420 code set deleted.

 

with the magnaflow you can run the 02 emulator (in the link I posted above) so the computer thinks it has a proper reading. Or I believe you can tune it out of the pcm so it won't register a code.
If you are planning on getting the tune for the pcm, which I highly recommend, I had mine tuned by Will @overkill and I also highly recommend his work, nice guy and the performance was worth it. Anyways if you are tuning, I would wait until you have any other mods done on the car so that you will get the best bang for the buck when you get the tune, as it will take all mods into consideration

 

X2....... Once you complete your major mods plan you can delete it amongst other things on the PCM, that's what I did and also got my tune from Will@Overkill, can't say enough about how pleased I am with his work...

 

I've been running a Magnaflow for over 2 years now with no code(s). I was prepared to use the spark plug anti-fouler trick, but didn't need to. A lot of people seem to experience a P0420 after swapping cats (no matter the brand). That makes me suspect that they have a problem elsewhere (such as fuel delivery, leaky exhaust, etc. that is triggering the code. A rich running engine can destroy a brand new cat in a very short period of time. Personally, I'd rather have the CEL illuminate so I can investigate the problem. If the code is tuned out you may be driving around not knowing the engine is in need of attention. That unattended malfunction can lead to further problems (or possible damage) to the vehicle.

Did you do a cooling system pressure test or cylinder leak down test to insure coolant isn't getting into the exhaust stream? As I mentioned in another thread the coolant can coat the internals of the cat triggering a P0420 code. A rich running engine can do the same thing. If you do install a Magnaflow just run with it for a while. It may not throw a code. If it does then address the problem. Don't put the cart in front of the horse.