Excessive Catalytic Converter failure

I have a 2001 Tacoma 4-door V6. I have burnt through 3 cats in about 3 years. I was told by multiple technicians that they should last the life of the vehicle. It all started when I had my back cat stolen (I HATE tweakers!!!). I've also been through a couple of O2 sensors. I have a 148,000 miles and I've been told my truck is just getting broken in. If that's the case, I'm quite naturally wondering what in the world is going on. I've told all the technicians that have worked on it to get to the ROOT of the problem. They haven't, so now I'm taking into my own hands. I am pretty good about regular maintenance, though admittedly I've got nearly 50,000 miles since my last timing belt and water pump change; I figured I'd replace the water pump when I change the timing belt since it will be exposed. I'm pretty sure the timing belt doesn't have much or anything to do with the cats going bad. If anyone can help me out in this area, it would be GREATLY appreciated!!!

 

Do you make it a habit of running out of gas, or is your engine running lean?
I'm not kidding... running out of gas on an EFI vehicle causes elevated cylinder temperatures as it leans out before it dies and this can damage the cat.

 

How do you know exactly that you are killing them?

 

What gas do u run? Crap gas kills cats.

 

Thank all of you for responding so quickly! I run 87 octane, but Chevron only. I know it's the cat(s) or O2 sensor, because my check engine light is on. All three of the last times it came on and I took it in, those were the error codes that came up. I used to run premium only from Chevron, but it didn't make a difference. I've been told by people I trust that having to run premium gas is a myth; that modern vehicles generally run efficiently enough and are designed to run fine on regular fuel. Albeit, these people I trust were not entirely Toyota enthusiasts, so I'm certainly open to the suggestion and the relatively small difference in price between premium and regular fuels isn't THAT big of a deal to me. It smells like it's running a bit rich, actually. I am admittedly ASSUMING that's why my check engine light is on, and we all know what assuming does. However, given that that was the reason the last three times, I figure it's a qualitative assumption. While on that topic as well, I've been considering purchasing an OBD-II module. I found one online from GHI electronics for about $60. It's costed me around $100 just to have them diagnose it each time, so I'm STRONGLY considering the purchase of my own module. Any suggestions? Again, thank you ALL, VERY MUCH!!!

 

Oh yeah, and I've NEVER ran out of gas. I usually fuel up before my gas light comes on. I didn't think that was a joke. Like I said I'm open to ANY suggestions. Thanks again!

 

First and foremost, as you already mentioned you should never assume anything when it comes to CEL and these trucks.

Second you need to get yourself a OBII handheld scanner so you'll know with a 95-98% accuracy what is causing the code, how to fix it, and how to reset it. I bought this one from Advanced Auto Parts for $70 and it's already payed for itself 10x over in the amount I saved by diagnosing and ultimately fixing the problem myself.



So unless you give us a code to go by, we can sit around and throw up ideas all day long. At least help us help you by narrowing it down, us Tacoma owners are pretty crafty when it comes to CELs.

 

Taco cats should last at least 130k. You getting p0420? Oem cats will also last way longer than aftermarket

 

I just got that code but the light went off on its own

 

I run every type of gas and have ran out of gas 3 times and I've ran my truck several times to the BARE minimum, I replaced my O2 sensor at 90k. O2 sensor will give 2 codes sometimes, keep this in mind!! I'm still on my original cat too. Bring some codes back so we can look them up for you!!

 

Sorry I should have been more specific.



-Your cat could be melted. hc: hydrocarbons (raw gas) these will melt the cat, and are usually caused from some form of misfire.
-your cat could be coated with some chemical ie: oil or other chemicals found in cheaper quality gasolines or additives such as sulphur Maganese,MMT. If this is the case there are actually ways to "burn off" the coating, such as giving the car a dead miss to get the cat hot enough to burn off the coating. (Toyota reccomended procedure)

-You could have coolant entering your combustion chamber. Thats Silicone.

-you could be burning oil in the engine and based on your mileage its definitely not a stretch. Having said that, your engine might be just as efficient as it was 100k miles ago...
-your cat could be broken, less likely if you keep having repeat failures.

And yes bring us your dtc's

 

I get the PO420 Code a lot and just use the OBD unit to turn it off. I have looked into buying a plug that will trick that back sensor to read correct and not ever get the code but I have yet to do this. Rick

 

Wow! You all are amazingly helpful; wish I would've joined a while ago. And, thank you Yamaha Dave! I will be getting one of those handhelds within the week. The last time I had it diagnosed it WAS P0420. I will post when I have a code for you all to work with. Thank you all...a MILLION!!!

 

Yes I remember that little trick. I may try that now that you have brought it to my attention.

 

Maybe you mentioned above, what brand parts are you using? Some aftermarket parts just are not as good, can't tell you how many aftermarket 02 sensors I have replaced in 0-2 years when the originals lasted 5 +.

Also I know it's prolly not possible but leaded full with wreck a cat & 02's quick.

 

you can rig your o2 sensors up to be tricked into thinking your cats working properly, cost about $10 and a hour or two of labor.

 

Alright. So, I bought an OBD-II handheld and the P0420 popped up as I thought it would. The cats that were replaced were aftermarket. The handheld read P0420 "catalytic converter inefficient (bank 1)". Should I replace the cat with a Toyota certified OEM converter? Also, I bought new NGK iridium plugs that I plan to install this coming weekend. Is it correct that the torque specs are 18-21 ft/lbs. It's been a couple of years since I've had my injectors cleaned, so I figured I'd do that as well. Any recommendations as to how to do that properly (by myself). My line of reasoning is that if it is running too lean, maybe there's an issue with my fuel delivery. However, as I said in my earlier post it smells a bit rich at the tail pipe. Thanks for all of the input; I cannot even begin to express how appreciated it is!! I love my truck, and want it to last as long as possible.

 

I think most people will recommend DENSO plugs, you can search around though and see. I think I have heard of some using some type of NGK plugs with no problems.