Diagnosing Cat vs. O2 sensors and replacement - 300K miles

[Miranthis]

Ok, I have a 2008 SR5 V6. Almost 300K miles. has a weird gas gauge issue and it ran out of gas recently. Refilled it and then got a pair of codes (P0420 & P0430) tried cat cleaning and O2 Sensor cleaning (several methods). Still get the codes. Wave forms on the Techstream show lots of variability, even when hot, on both downstream sensors. Lambda is either side of 1 (0.98 - 1.02, variable) on both banks, LT Fuel trims are less than +3% both sides. Upstream cat temps are 12-1300 +/_ and downstream are 10-1200, which matches 2 other known good vehicles with no CELs or codes thrown.

I can't find any online confirmation that running out of gas kills cats, but yet here i am. :frusty:

I replaced an O2 sensor with a Denso from Rock Auto 1.5 years ago after it threw a code and the old one failed the checks.

I am about resigned to doing the Cats and with them the downstream O2 sensors, just cause of the mileage. Any ideas on narrowing this down? I am going to do the exhaust leak check tonight, but unless there is a leak between the two sensors (especially between the cat and O2 sensor) its not supposed to make a difference, right? :help::frusty::help:

Guess my question is, every experts says, generally, that cats "last the life of the vehicle", and then talk about typical US car lives (less than 200K). For those of us that drive them past 300K, how long are the cats lasting? I have driven camrys, a sienna and this 4runner all past 300K and i have only one replaced a cat...on the sienna after an A/F sensor shot craps, slowly, and it ruined the cat.

And when I do the cats, i am looking at the usual aftermarket folks with 2 - 5 year warranties, which should be good enough, but who should I avoid?

Thanks in advance,

Jeff-in-KC

 

[MikeinNH67]

Seems odd that you'd have both cats fail at the same time. Exhaust leaks do create these codes and you probably know searching around. Fix that first of course. Pressurize the system with something lowish PSI and quiet then listen for leaks. Mine leaked at the manifold to engine area on one side, the manifold was no longer strong enough to seal. Another common place is where the 2 sides come together.

The upper cats are not easy to remove, at least in the Northeast. As for aftermarket, buy from a reputable place and one that has a good warranty. I went with one from Rockauto. I also looked for one with a strong looking flange on the engine side, if I have to I'll weld the old cat section onto the new pipe. One other thing, if you do replace them try to recoop some $$ selling your old ones to a recycler as OEM cats are worth money unless they are hollow of course. Good luck.

 

[Miranthis]

I am gonna do the leak test today. It also seems odd to have both fail at the same tim, especially as it happened right after running out of gas, and that does not appear to be a noted cat killer. To make it more complex, i always get thr p0420 first and then minutes, trips,or miles later p0430 comes on. The wave forms loom different between them on techstream, but my copy has a slow refresh/sample rate so the date is not as useful as it could be with a faster sample rate.

I have already been spraying down the nuts and such with various pen oils, just in case.

If the leak test is negative i think i will replace both downstream sensors (one is original) as i would do that anyway with a cat change, and see if that changes the wave forms on Tech stream. If not, it is likely the cats. This is why i wondered what the magic mileage was for cats as i am basically at 300k.

Seems that any shop is just gonna throw new cats and all o2 sensors on it anyway and call it good. Wish i knew a mechanic that would look hard at this and not just do the standard fix...or at least humor me by letting me see the data and maybe do a propane test to check remaining o2 storage capacity .

 

[Miranthis]

Did a leak test and no leaks at all between the downstream cats and the engine. I have a tiny pin hole leak in the gasketed coupler between the resonator and the muffler. Will replace that gasket as well, but unless someone says otherwise, I am going to try new O2 sensors and if that does not fix the waveforms, I think it has to be cats.

Anyone else have something I should try? I would love to do a O2 storage capacity test, but with a 1000 - 2000 ms sample rate the data is useless for that as a new cat has between 2 and 4 s of storage at best and even 90% of that is within the error of the sampling rate.

 

[BMeister]

My cats went around 219k miles but this was because I had the stupid HG leak. I tried replacing everything cheap (o2, gaskets, exhaust, etc) but the p codes kept coming back till I replaced the cats.

 

[plutonic]

OK, so this is an old subject but my search-fu has failed me and I have questions.

Couple of weeks ago I got the check engine light with the traction control lights on and a P0031 code, bank 1 sensor 1 failure.
Changed the sensor, changed the gas cap, car worked fine for about an hour or so, then got the same s*it again.

What could be the problem? Catalytic converter went bad? Manifold leak? What do you smart people say, what else could be the problem?

Thanks!