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Why o why did my beloved Toyota design an exhaust system to fail?? Seriously, they HAD to know the forward cats would fail so did they make them replaceable? Nope, instead they made them part of the exhaust manifold!!:flame:

I love the FJ and have very few gripes with it, but this is the biggest problem I have seen to date. My dad has an '05 Taco with the same 4.0L V6 and with less than 100K on the odometer we have already had to replace the exhaust manifolds because the forward cats have failed. Not cool Toyota, not cool.:mecry:
 

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Thanks for posting this..
That's not good news, but in the interest of seeing the silver lining.. it presents a good reason to put headers on with some new cats when they do fail.. Right..??
For future reference, how did they fail? What were the symptoms?
 

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cats are warranteed (don't quote me on this) for 50,000 miles by law on all CARB vehicles. Luckily for us, the manifold isn't welded on, so we can unbolt, replace cat, weld it in, and bolt her back up good as new...
 

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Remove them permanently will be my solution at some point.
Some o2 simulators are easily plugged in to the rear o2 harness plugs to fool the computer into keeping the trouble code away.
Our state of WA doesnt check for the physical presence of cats at the emission test UNLESS you are attempting to get a repair waiver after you fail. So if you pass- no problem.
I think its the forward cats that are "monitored" by the rear o2 sensors. I have a feeling the failure symptoms may have been just a check engine light with a catalyst efficiency trouble code- meaning theyre not plugged up, but the substrate material is just plain ineffective. There would be likely no performance issue with this type code.
 

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Some long tube headers will solve that cat problem, although it isn't quite street legal.:rocker:
 

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Why o why did my beloved Toyota design an exhaust system to fail?? Seriously, they HAD to know the forward cats would fail so did they make them replaceable? Nope, instead they made them part of the exhaust manifold!!:flame:

I love the FJ and have very few gripes with it, but this is the biggest problem I have seen to date. My dad has an '05 Taco with the same 4.0L V6 and with less than 100K on the odometer we have already had to replace the exhaust manifolds because the forward cats have failed. Not cool Toyota, not cool.:mecry:
In some states (CA, NJ?) I thought the cats were covered by the warranty for 100K miles.

DEWFPO
 

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Discussion Starter #9
Remove them permanently will be my solution at some point.
Some o2 simulators are easily plugged in to the rear o2 harness plugs to fool the computer into keeping the trouble code away.
Our state of WA doesnt check for the physical presence of cats at the emission test UNLESS you are attempting to get a repair waiver after you fail. So if you pass- no problem.
I think its the forward cats that are "monitored" by the rear o2 sensors. I have a feeling the failure symptoms may have been just a check engine light with a catalyst efficiency trouble code- meaning theyre not plugged up, but the substrate material is just plain ineffective. There would be likely no performance issue with this type code.
Yep you nailed it, a check engine light is thrown but there are no physical symptoms. It's just a PITA to get rid of the check engine light. In the Taco we did just replace the front cats with long tube headers, and it was over 50K miles.:mecry:
 

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I just put Doug Thorleys on and it was a sheer hellish nightmare getting the factory manifolds off. Access is very very close to impossible on the left side. It is a coin toss whether you try to tough it out or remove the engine first.
 

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I think this is the same problem I am having with the front converters going bad prematurely (38k Miles). I have the check engine light with a catalyst efficiency trouble code-but worse than that, for some reason it disables critical safety features such as traction control, stability control,ect.

Why in the hell would Toyota disable these based on a converter issue? I have had some dangerous rainy day sliding and really need to get this fixed.
Of course I'll have to re-install the factory y-pipe w/cats and remove my uni-chip to get it fixed under warranty......:mecry:

Any suggestions, ideas. No flaming for removing rear cats, that wouldn't affect the fronts, and as far as the uni-chip, well okay, maybe a contributor...
 

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The federal warranty on emissions is 8 years or 80k miles on specific components including the catalytic converters.
My FJ's catalytic convertor went bad with less than 27K miles, and the dealer told me the same thing on the warranty side (8/80K).
 

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Both my fronts went out around 50k. Within a week of each other. At least I have a full new emmissions system, including the rear cat. Putting them in the manifold is err..uhmmm...unique, at least for Toyota.
 

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Bringin this thread back from the dead as I am about to replace my Exhaust manifolds due to O2 sensor codes (yes we've narrowed it down to the manifold). It's the only thing left that could be causing it (I'm just past 300,000km), my issue came from getting contaminated gas from a station (screw you petro-can) that had some diesel in it. We reckon that the diesel ignited in the exhaust manifold and crunched the honeycomb cat or something.

Do you guys have any tips for removing them or tricks that I should know? I have begun spraying the bolts with penetrating oil to soften them up and taking a wire brush to the rust before I begin (planning to perform the operation on June 11th).
Is it safe to move the AC lines out of the way (considering they're metal of course, my default is no but you guys seem to have done this before)?
I am gonna take pictures as I go to ensure I put everything back properly and maybe to make a pics DIY thread.

Cheers!
-BigFish96
 

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From my knowledge Toyota recommend using Hi octane gasoline on Fj Cruiser for proper emissions function. What gasoline was used on Cat felled. Just curious about this problems.
A friend of mine just got a 2014 Fj Cruiser and advice him to used super gas only.He never take my advice seriously and fill regular.
See how long his emission last.Got mine at 181.000 and no one issue yet.
 

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It will be interesting to see if the posters to this thread from 11 years ago answer.

Regarding grade of fuel: regular, or premium, won't make any difference in CAT life. Contamination, on the other hand, of the fuel will.

Sometimes, mechanics reflexively replace the CATs when the OBDII code says there is an issue with the "CATs", instead of confirming that it isn't something simpler first (like failed O2 sensor, etc.). Typically, one that hasn't been subjected to contaminated fuel will last for several 100k miles before any trouble (and then, it is often rust of the housing, rather than issues with the matrix inside).

N
 

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It will be interesting to see if the posters to this thread from 11 years ago answer.

Regarding grade of fuel: regular, or premium, won't make any difference in CAT life. Contamination, on the other hand, of the fuel will.

Sometimes, mechanics reflexively replace the CATs when the OBDII code says there is an issue with the "CATs", instead of confirming that it isn't something simpler first (like failed O2 sensor, etc.). Typically, one that hasn't been subjected to contaminated fuel will last for several 100k miles before any trouble (and then, it is often rust of the housing, rather than issues with the matrix inside).

N
Rust kills cats? Uh oh I’m doomed.....
 

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It will be interesting to see if the posters to this thread from 11 years ago answer.

Regarding grade of fuel: regular, or premium, won't make any difference in CAT life. Contamination, on the other hand, of the fuel will.

Sometimes, mechanics reflexively replace the CATs when the OBDII code says there is an issue with the "CATs", instead of confirming that it isn't something simpler first (like failed O2 sensor, etc.). Typically, one that hasn't been subjected to contaminated fuel will last for several 100k miles before any trouble (and then, it is often rust of the housing, rather than issues with the matrix inside).

N
I just had mine replaced. After this, the next time it will be headers and a rework of the whole exhaust setup. Toyo was nuts to make the exhaust manifold and cats one piece. And remember my mileage Norm - HelTeef ain't no spring chicken....;)
 
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