Anyone know how to Gut The Pre-Cat?

A

ayang89

Member
:
2003.5 Mazdaspeed Protege #1827
My car just through a p0421 code. Fix one code, another pops up.
Don't have extra cash laying around for a new one.

Anyone know how to do this step by step?
It's my daily and I've been reading if I keep driving with my pre cat clogged I'll go zoom zoom boom.

DONT WANT THAT TO HAPPEN

If somebody can help with a picture as to what or where its located and a basic step by step. It'll be much MUCH appreciated.

Also a non-fouler if I'm correct? Step also please.

Thanks!
 
I just had someone cut them out and weld in straight pipe. Alternately buy an sls midpipe.

Even better, you live in or. Drive to corksport and buy one of their exhaust. 2.5" was like $400.
To save even more money just stay out of the boost.
 
Last edited:
The_big_dill said:
So you have a turbo and a pre-cat?
Click to expand...

I was reading on some other forums that were saying the proteges have 2 cats. I have a straight pipe after the turbo where I believe the o2 sensor and cat is suppose to be. But its just a straight pipe with a bung for the o2 to plug into.

I'm throwing a p0421 code. Which is the cat warming up to hot right?

But like I said, no bottom cat after turbo. Unless I'm wrong somewhere.
Took out the 2nd o2 sensor ( not the one on the manifold ) and it was clogged up good with crap on it. I cleaned it up and put it back in.

Seems like my exhaust is spitting out little pieces of black crap when I start it. ( its on my garage door and little bit misted on my back bumper )

Unless, There isn't another cat and my second sensor was just crap. Which ill have to do the spark plug non fouler trick if there isn't another cat.

I don't know how to post up pictures otherwise I would hah.

First MSP. Been in the Honda scene for a long time. This is a new game for me.

Sorry for being a noob.
 
P0421 is probably the second O2 sensor. Just because it throws a code doesn't mean the cat is bad. Spark plug non-fouler trick is what most people do on these cars when they are catless.
 
ayang89 said:
I was reading on some other forums that were saying the proteges have 2 cats. I have a straight pipe after the turbo where I believe the o2 sensor and cat is suppose to be. But its just a straight pipe with a bung for the o2 to plug into.

I'm throwing a p0421 code. Which is the cat warming up to hot right?

But like I said, no bottom cat after turbo. Unless I'm wrong somewhere.
Took out the 2nd o2 sensor ( not the one on the manifold ) and it was clogged up good with crap on it. I cleaned it up and put it back in.

Seems like my exhaust is spitting out little pieces of black crap when I start it. ( its on my garage door and little bit misted on my back bumper )

Unless, There isn't another cat and my second sensor was just crap. Which ill have to do the spark plug non fouler trick if there isn't another cat.

I don't know how to post up pictures otherwise I would hah.

First MSP. Been in the Honda scene for a long time. This is a new game for me.

Sorry for being a noob.
Click to expand...

you should have a pre cat and then a cat. one after the down pipe and then one farther down. the black crap starting is normal. if you upload pics to imgur or photobucket there should be a little
 
littlemimus said:
you should have a pre cat and then a cat. one after the down pipe and then one farther down. the black crap starting is normal. if you upload pics to imgur or photobucket there should be a little link that you just copy and paste onto the forum and it will display your picture.[/QUOTE]

Ok thanks. I'll take some tomorrow n put one up for you guys to see it.
Click to expand...
 
hornsfan10609 said:
P0421 is probably the second O2 sensor. Just because it throws a code doesn't mean the cat is bad. Spark plug non-fouler trick is what most people do on these cars when they are catless.
Click to expand...

Yeah that's what I was thinking. Cause the sensor was all clogged. I'm guessing from my turbo seals going out and it started smoking through my exhaust sometimes n clogged it? That's my guess.
 
I get that code every once and a while. It goes away after a few drive cycles. It has no bearing on drivability. I have not had the catalyst pipe on my car for almost 10 years now. I do have a non-fouler in place. I'd say my 2nd O2 sensor is failing but I don't give a s*** about it as its absolutely worthless on my set up.
 
That's strange, I don't have a pre-cat in my MSP but then again, it could've been removed by the previous owner. Not sure in an MSP but when I had my 626, I had the mechanic remove the pre-cat when upgrading the exhaust and it never gave me any issues. Even passed emissions without it. So I'd say, get rid of it and don't look back. The P0421 sounds like an O2 sensor code so I'd start there. Do you know if your cat is ok btw?
 
njintau_fsd said:
That's strange, I don't have a pre-cat in my MSP but then again, it could've been removed by the previous owner. Not sure in an MSP but when I had my 626, I had the mechanic remove the pre-cat when upgrading the exhaust and it never gave me any issues. Even passed emissions without it. So I'd say, get rid of it and don't look back. The P0421 sounds like an O2 sensor code so I'd start there. Do you know if your cat is ok btw?
Click to expand...

I have not owned an MSP but just from observation, I see a turbo where a pre-cat would typically go.
 
njintau_fsd said:
That's strange, I don't have a pre-cat in my MSP but then again, it could've been removed by the previous owner. Not sure in an MSP but when I had my 626, I had the mechanic remove the pre-cat when upgrading the exhaust and it never gave me any issues. Even passed emissions without it. So I'd say, get rid of it and don't look back. The P0421 sounds like an O2 sensor code so I'd start there. Do you know if your cat is ok btw?
Click to expand...

Well that's the thing. I can't find any pictures of a stock exhaust system off a MSP to tell where the difference is between my set up n factory. I'll post pictures in a bit.
 
There are plenty of pics on here with the factory exhaust set up. Many people, including me have posted pics of it along with what went in to replace it.

Good news for you, no need to worry about gutting any cats as you have none on your set up. Your catalyst pipe has been replaced with a straight pipe. It does look like you have the factory resonator piping in place.

So your P0421 is absolutely meaningless as you have no cats which can be below the warmup threshold. Most likely you have a failing or failed 2nd O2 sensor. If you do not have the non fouler in place you can do that. You'll need the HELP Product kit and a drill with a 1/2" bit. Install that and try cleaning the sensor, clear the PCM and see if the CEL goes off. Either way that CEL will not impact the drivability or make you join a club that you do not want too!
 
BOOSTR said:
There are plenty of pics on here with the factory exhaust set up. Many people, including me have posted pics of it along with what went in to replace it.

Good news for you, no need to worry about gutting any cats as you have none on your set up. Your catalyst pipe has been replaced with a straight pipe. It does look like you have the factory resonator piping in place.

So your P0421 is absolutely meaningless as you have no cats which can be below the warmup threshold. Most likely you have a failing or failed 2nd O2 sensor. If you do not have the non fouler in place you can do that. You'll need the HELP Product kit and a drill with a 1/2" bit. Install that and try cleaning the sensor, clear the PCM and see if the CEL goes off. Either way that CEL will not impact the drivability or make you join a club that you do not want too!
Click to expand...

Alright thanks! Really good to know that. I'll do the non-fouler trick in a bit here. Gotta grab the supplies. Really glad I don't have to gut anything or joining a club I don't wanna be in lol.
 
The HELP spark plug anti fouler kit you want is #42002. Advanced, AutoZone or O'Reilly's should have it.
 
Though it doesn't matter, I use the 42009 Dorman as opposed to the 42002- they're both 18mm but 42002 is taper seat.
 
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