Replace Front Catalytic Converter Questions

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chevelles240

:
2002 Mazda Protege5
Hey Gang,

So a Mazda dealership informed me I would have to replace my front catalytic converter to the tune of $1232, not including labor. That's a crazy price in my opinion so I'd rather attempt replacing it myself or have a third party auto-mechanic replace it. I'd rather install a new one than remove it and not install a replacement.

Do any of you recommend a type of catalytic converter I should get? I found this one online and it seems legit:
http://www.autopartswarehouse.com/shop_parts/catalytic_converter/mazda/protege5.html

Should I clean/replace anything else in the process of pulling this one out? Would I probably need to weld anything or are "direct-fit" converters basically plug n' chug? Lastly, dumb question, is the front catalytic converter called a pre-cat? (my auto mechanic knowledge is really shining now. (lol2))

EDIT: To be clear, I've been getting the P0421 error code.
 
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You can fool it with a pair of 18mm spark plug non-foulers. Search for the process, it's well documented. You can even pass emissions testing with it, if your secondary cat is working. You won't hurt a thing by running it this way, the #2 oxygen sensor is only there to monitor catalyst function.
 
MrGiggles said:
You can fool it with a pair of 18mm spark plug non-foulers. Search for the process, it's well documented. You can even pass emissions testing with it, if your secondary cat is working. You won't hurt a thing by running it this way, the #2 oxygen sensor is only there to monitor catalyst function.
Click to expand...

This only hides the underlying problem, right? I was told the 02 sensors were fine but wasn't given any specifics on what's wrong with the converter itself. The non-fouler trick serves as a way to get rid of the engine light?
 
chevelles240 said:
,... This only hides the underlying problem, right? ...
Click to expand...

The pre-cat is a very thin delicate cat that heats up faster and starts working sooner than the regular cat.

But only for the first couple of minutes until the main cat heats up and starts working.

It serves very little purpose and only reduces pollution for a minute or two during warm up.

The non-fouler trick doesn't just prevent the code, it takes the engine out of "limp mode". When the car is in limp mode it's gutless and wastes all kinds of gas (which is the ECU's way of protecting the engine).

If you're worried about wrecking the environment with the non-fouler trick, the amount of actual pollution is VERY small.
 
pcb said:
The pre-cat is a very thin delicate cat that heats up faster and starts working sooner than the regular cat.

But only for the first couple of minutes until the main cat heats up and starts working.

It serves very little purpose and only reduces pollution for a minute or two during warm up.

The non-fouler trick doesn't just prevent the code, it takes the engine out of "limp mode". When the car is in limp mode it's gutless and wastes all kinds of gas (which is the ECU's way of protecting the engine).

If you're worried about wrecking the environment with the non-fouler trick, the amount of actual pollution is VERY small.
Click to expand...

Well, I'd save a ton of money by doing the non-fouler trick and I do not have the patience nor desire to get raped by the dealership again. I've already invested too much money into this car in JUST maintenance and repairs. If I do end up replacing the converter then I would do it myself as a summer project. It's insane how much something with little significance costs so much for the dealer to take car of.
 
If you're not worried about visual inspections, it may be cheaper to put a header in place of that cat. You'd still have the second cat in place, and you might be able to get by with some creative header wrap for any looks under the hood.
 
chevelles240 said:
To be honest, I'd rather keep the car as stock as possible and keep everything that "should" be on it. I watched this video: https://www.youtube.com/watch?v=5icTmYItwiE

I am thinking of trying this too.
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I watched the video but I don't know if that will help you. In fact the cleaner (lacquer thinner) may destroy the pre-cat the same way two minutes of raw gas can.

As far as I know, the pre-cat tends to disintegrate not plug up. You may not have any honey comb left inside to clean. (remember it is very thin and delicate unlike other cats.)

Your best bet is still to do the non-fouler trick,... cheap and easy and you don't have to take your exhaust apart.

It will look completely stock except your second O2 sensor sticks out an extra inch.



On a bit of a side note,.. I used lacquer thinner once on my '85 626 and it partially dissolved the rubber on a solenoid controlled plunger thing in my carb and made it sticky so it wouldn't release.

Ethanol in the gas can also affect seals and such but newer cars use better rubber that is more solvent proof (probably polyurethane)
 
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I probably wont add lacquer thinner to my gas tank then.

If I do go through with the replacement route could any of you tell me if anything is welded between the exhaust manifold and pre cat? Is it welded underneath the pre cap and where it goes underneath the car too? I looked at it with a flashlight but there is a heat shield wrapped around the converter, so I wasn't able to get a clear look as to whether the converter is bolted, clamped, or welded on.
 
It's all nuts and bolts man.

Give them a good soakin' with some sort of penetrating lube some time before you attempt removal. There are also a couple of gaskets that I would replace, on both ends of the pre-cat.
 
I'm running a 4-2-1 header with a single minicat installed just behind. The cat included a bung at the back for the second factory O2 sensor; the first (which went into the OEM garbage can precat on the factory header) plugs directly into my 4-2-1. Behind the minicat is a Magnaflow resonator into a short length of pipe. Behind this is a Magnaflow catback with twin tips. All pipe is 2.5". When dynoed, I gained 8+ WHP and a corresponding increase in torque.

This mod passes very stringent Colorado emissions testing with flying colors--the numbers in all categories are extremely low. The system has been in the car for seven years w/o problems of any kind. The sound is unlike any other IL4 I've heard, low and very civilized--no fart can rap or other "look at me" noise.
 
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So I had a nice big hole in my pre cat and bought this m2/manzo header to replace it....those nuts look welded to the flange on the mid pipe with the cat. The bolts are so rusty they're not budging. I'm either going to have to use a dremel to shave the nuts off and use the new ones, or drill through the bolt inside of it and use the existing nut that's welded on. Does anybody have any suggestions? Thanks!
 
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