How do you remove / replace the catalytic converter?

[51steve]

Hello Everyone,

I've got a 2000 protege that now has 158k repair free miles on it (ok the camshaft sensor went out last year- do 5 min repairs count?)

The check engine light went off- and the code was for the catalytic converter- verified by the mazda dealer. There are no other codes at all. The haynes manual is useless. How do I remove/replace the converter and the manifold heat shield?

Before doing a repair I always look around to see where problems could arise before I do anything- well the bolts that attach the heat shield to the manifold seem to be the first problem. They are corroded and pitted and the fit is sloppy on the socket. I've been using PB blaster to no avail- and I don't want to shear the bolts off. What do I do?

So as a back up plan, if in fact I do shear off the bolts, I contacted a machine shop to see if the would be able to retap/clean out the threads in the manifold. The shop said that it is often easier to remove the whole manifold from the block with the converter attached and disassemble on the bench. Which, after looking where the five bolts that attach the converter to the manifold seems like it might be the case.

Also, there are a lot of aftermarket converters. How do these stand up to Original Equipment?

I will post my progress to the "how to" section of this forum, since other people will have this same problem in the future.

Thanks,

Steve

 

[51steve]

Well, I've be looking around and it cost $125 for an exhaust shop to cut out the old converter and weld in a universal. Has anyone gone this route? Saves me the time of doing it myself.

 

[ucMP3]

I think that sounds about right... A high flow cat on the web would run you a little over $100 (in general) and then I would guess $40 or so for a shop to weld it/install it. So, $125 seems pretty accurate for a universal. I've never had it done tho, and prices will vary by location.

 

[BMXbmw]

Hey Steve. You didn't mention if you had a ZM or FS. But here's a pic of the ZM (1.6) for ya. This should give you some of an idea. I just had my cat out while I was replacing the exhaust manifold. The bolts holding my heat shield on were fine, but the bolts on the bottom heat shield (under the car) were a little rough. One was so bad that it did round off loosening it. I got it off by dremeling some of the metal off on six sides so I could step it down in socket size and get a good grip on it. You only really get one shot though because at that point the metal is so weak. It did come off though. PB Blaster at this point is also a must. You can get the heat shield off by loosening the bolts, unplugging the O2 sensor then sliding the heat shield out of the engine compartment while the harness side of the O2 sensor is coming out the hole of the heat shield. Now you can take a 7/8" or 22MM wrench and remove the O2 sensor from the exhaust manifold to get it out off the way. The rest is just nuts and bolts from there to get the cat out.

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[51steve]

Thanks everyone for your responses. It looks like I will take a jump of faith and have the muffler shop put in a universal. Do they need to take out the O2 sensors before cutting and welding due to the heat? Or are the O2 sensors far enough away? This will be the second person beside myself that has worked on the car, and I worry.

Steve

 

[lilpoindexter]

What was the code you had?

 

[2000MAZPro]

hey my cat went out on my 2000 protege..i solved the problem by buying a new cat off ebay for $100 and installed it myself. It was fairly easy to change, only took 2 hours or so. The only thing I needed was a new gasket for the spot where the cat and the manifold connect, which i got at the dealership. Its been 1000 km now and so far so good...i'd recommend doing this to fix the problem, it wasnt to hard and didnt cost much.
http://cgi.ebay.ca/Mazda-Protege-99...4295230QQihZ010QQcategoryZ33629QQcmdZViewItem

 

[MS3_KIDD]

What was the code you had?

id like to know this as well
theres no such thing as a bad cat code

 

[prof15]

So there are 2 CAT converters on the Protege's? If so, is there a way to tell which one is bad? I have 2001 ES and it got a CEL and it say it is the CAT so I am looking into get it replace it with an universal or with the original.

 

[MS3_KIDD]

replace both, thats what anyone else would do in this situation
and after the 4th or 5th cat on the vehicle they'll finally figures, hey maybe the cat wasnt the problem


i know for a fact the code doesnt say the cat is bad


the code you must be refering to is a P0420 and the global OBDII description is Catalyst Efficiency Below Threshold

I dont have time to tell you all the possible causes but i can tell you if the cat is actualld bad, go find you problem cuz by replacing the cat you are only fixing the effect of the problem

Take that from someone whoes spent the last 2 months (6hours a day/5 days a week) in a engine performance course and well spend the next 2 months in a Advanced Engine Performance course (L-1)

food for thought:
http://www.obd-codes.com/p0420

 

[51steve]

Hello Everyone,

Yes, it is the P0420 code. When the engine light first went on I took it to an auto parts store, and they pulled the code P0420 (they said most likely cat converter). So instead of just putting in a cat converter I went to the professionals (say what you like) at a Mazda dealership to verify that it is in fact a catalytic converter. They pulled the same code (WOW) and I asked if there were any other codes, they said no, no other codes- nada. I asked if it was common for a cat to go, and what causes a cat converter to go and they said, sometimes they just go.

So, either my converter just went or there is an underlying cause.

Protg kid, (or anyone else) if you have a moment, could you tell me the normal causes for cat failure? I assume something with the combustion of fuel (the reason for a converter). Ive replaced plugs and wires with original Mazda parts, as a part of normal maintenance. The only other thing I could think of is the coil packs.

Ill get back with everyone tomorrow, thats when I get the universal put in.

Steve

 

[MS3_KIDD]

after reading what i wrote this morning i kinda feel as if i were alittle mad at the time and appologize if i offended anyone with my OBDII tirade lol

now while cats sometimes do "just go", due to the enabling criteria (what the PCM looks to see that meets the requirements to set a code) there could be other factors that play into setting the code



While running the Catalyst Efficiency Monitor the PCM looks at the upstream
O2 sensor and watches the switching and looks at the downstream O2 sensor to be steady

It will set the code if the values are within a certain percentage within eachother

Thats pretty much the crash course on a P0420 with some stuff assumed of course
(vehicle must have met the requirements to run the cat. eff. monitor, etc)

 

[BMXbmw]

Hello Everyone,

I've got a 2000 protege that now has 158k repair free miles on it

Thanks,

Steve

Steve, Has either O2 sensor been changed? The service interval 4 replacement [at least on protege] is 100,000. My car had cel on when I got it [same code as yours]. Was told before I bought it the O2 sensor was bad which was causing the cel. Replaced downstream O2 sensor. cel gone. I'd change the O2 sensors if they haven't been done yet [since they're due anyway]. Maybe the cel will even go away.

Ryan

 

[slavrenz]

hey my cat went out on my 2000 protege..i solved the problem by buying a new cat off ebay for $100 and installed it myself. It was fairly easy to change, only took 2 hours or so. The only thing I needed was a new gasket for the spot where the cat and the manifold connect, which i got at the dealership. Its been 1000 km now and so far so good...i'd recommend doing this to fix the problem, it wasnt to hard and didnt cost much.
http://cgi.ebay.ca/Mazda-Protege-99...4295230QQihZ010QQcategoryZ33629QQcmdZViewItem

Yeah, I don't think I would trust an ebay converter - no matter what they say, there's no way there can be more substrate in a $100 converter versus a $750 one.

Walker does make a direct fit converter for our cars that is on RockAuto.com for about $250. I am currently using it, and it performs close to OEM, and comes with a 5 year, 50,000 miles warranty. I don't remember the p/n, but go to RockAuto.com to check it out.

 

[BMXbmw]

^^^^ +1 I've bought many parts from them [for my last car... constantly needed parts]. Some great deals.

slavrenz, I looked up that part number...

WALKER Part # 16213 {Direct Fit} $262.89

 

[prof15]

after reading what i wrote this morning i kinda feel as if i were alittle mad at the time and appologize if i offended anyone with my OBDII tirade lol

now while cats sometimes do "just go", due to the enabling criteria (what the PCM looks to see that meets the requirements to set a code) there could be other factors that play into setting the code



While running the Catalyst Efficiency Monitor the PCM looks at the upstream
O2 sensor and watches the switching and looks at the downstream O2 sensor to be steady

It will set the code if the values are within a certain percentage within eachother

Thats pretty much the crash course on a P0420 with some stuff assumed of course
(vehicle must have met the requirements to run the cat. eff. monitor, etc)

The code that I have is the P0421 which I guess is the same as the P0420 since the description is "Cat system efficiency below threshold".
and exhaust leak, and Faulty cat converter as possible causes.

Do you think I should take the car to a shop to find out the main cause? because I just found out in another thread that the only cat that is monitored is the first one, so in that case I was thinking on replacing it with an OBX header since it will be about the same price of getting a new Cat.

 

[slavrenz]

If you've got no emissions testing in your state, and you're not a tree-hugger (I say that with complete respect - I am one who replaced my failed converter instead of going to a header), I'd say go for the header. You may still be able to get by with the header if PA has emissions inspections, but sometimes they have a visual inspection of your cats that you could fail with a header on.

You could also just do the nonfouler trick for now if you want to save up for a new converter/header and you want the CEL off.

 

[slavrenz]

^^^^ +1 I've bought many parts from them [for my last car... constantly needed parts]. Some great deals.

slavrenz, I looked up that part number...

WALKER Part # 16213 {Direct Fit} $262.89

There you go. Just realize that the Walker converter will probably not last much longer than the 5 year, 50,000 mile warranty, but it will suffice as a decent replacement for a while. To my understanding, the markup on OEM converters is very little - they are so expensive because they put much more catalyst into them than the aftermarket converters.

After all, by federal law, the OEM converters have to last 8 years or 80,000 miles.

That said, Walker does make great quality products (I am also running their Quiet-Flow muffler with a lifetime warranty, and it sounds like OEM), so I will report back in 4 1/2 years to say how my converter is holding up

 

[prof15]

If you've got no emissions testing in your state, and you're not a tree-hugger (I say that with complete respect - I am one who replaced my failed converter instead of going to a header), I'd say go for the header. You may still be able to get by with the header if PA has emissions inspections, but sometimes that have a visual inspection of your cats that you could fail with a header on.

You could also just do the nonfouler trick for now if you want to save up for a new converter/header and you want the CEL off.

Thanks for the info...I will try the non-fouler for the mean time just to get cel off like you suggested. We do have an emission test in PA, but I am not sure if they also do the visual one.

So what is the function of the second cat on this car? because if the first one cleans the exhaust gases, do the second one do the same? This is the first time I see a car with tow cats, I actually was thinking on replacing the second one since that is the one I normally see in cars.

 

[slavrenz]

Yeah, the second cat is just extra protection I guess against bad emissions. From what I've heard from other members on this forum, this rear cat alone is sufficient to clean your exhaust to bring it within acceptable emissions specs.