Catalytic Convertor Failure

I'm looking for some advice as to the root cause of my third driver side catalytic convertor failure. My 2007 LBDC 5.7 has 370,000 miles on it and still going strong. HOWEVER, I've had a nagging issue with the driver side only convertors failing. The original went starting with an error code pointing to CC inefficiency (I don't know what the code # is). With the code present, we were returning from a trip pulling the fifth wheel up I75 at Jelico, TN running the speed limit just fine, but once we topped the grade and I dug the accelerator out of the floor mat, it sounded like there was a large rock banging inside the exhaust. Catastrophic fail of the element I supose, and I elected to replace both sides with Magnaflow cats, which were a noteable improvement in performance and fuel milage. After about 9 months, the CEL came on again with the same code indicating inefficiency of the same cat. Magnaflow replaced that cat under warranty, but the code came on again after about a year or so and I just ignored it.

Yesterday, I noticed the all to familiar sound of the CC element banging around again, so I have to replace it yet again. I've replaced both sets of O2 sensors on both sides a few times over the years with Denso, so I don't think they are the culprit. There has to be something I'm not aware of to cause these failures. @ViktorG, @Wynnded do you or anyone have any ideas?

Thank you in advance!

 

P0420 and P0430 are the cat inefficiency codes that I'm aware of. Each code points to one side of the engine or the other, Bank 1 or Bank 2. I have to be frank and say that I really don't have much experience sorting out converter issues. I'm just shadetree and any experience that I might have is due to me having to fix my own stuff. I know that a really rich burning engine can wreck the cats, but I would think that there'd be other obvious warning signs, like check engine lights telling you that. Bad gas could probably do it, fuel additives could probably do it too. I've read here that Tundras are pretty sensitive to aftermarket cats, that seems to produce various codes though as well. If the spark plugs are old, that could certainly impact fuel burning efficiency adding unburned fuel to the exhaust that the cats have to deal with which could shorten their lives. Pulling a big honking trailer up a mountain pass on the regular would put the engine in an Open Loop condition where the ECU ignores the O2 sensors and the engine runs rich. The Tundras also have a system that tries to protect the cats from getting too hot by dumping even more fuel into the engine to cool them.

With that bit of random rambling, I'd see if @Ruggybuggy would have any sage advice, if he doesn't mind.

 

@Wynnded , thank you for your quick response and reaching out to Ruggybuggy. Any input is greatly appreciated!

So I've religiously kept up on routine maintenance including replacing the plugs every 125K. Coming up on that again in a couple months with 370K today.

I will say that until last month, I only used 92 octane fuel or higher thinking it was the cleanest and best for the truck and offered improved MPG. I guess the "New Truck" feeling has now worn off and I started using 87 octane. I cannot see any difference in MPG or power and I'm really wondering if I didn't blow $$ on high octane with no real benefit over these fifteen years. Plus to add insult to injury, could this possibly have contributed to the cat fails???

I'm going to order another Magnaflow cat and go from there on 87 octane only. Other than these aftermarket cats, there are absolutely no other mods or replacement parts over OEM on this truck, so there shouldn't be anything else beyond stock that is contributing to this problem, save a problem somewhere with performance of a component(s).

My eyes and ears are open to any advice!

 

No problem.
I had to ask what I thought might be relevant questions. The more data the better. I'm sure that there'll be more.
I think that your fuel choice is unlikely to have been the problem. The extra money spent is water under the bridge.

 

Things like unburnt fuel over heating the cat will cause them to fail. It could be something simple like plugs that need changing or a little more involved like a coil pack or injector not working right but not bad enough to cause a fault code. Another possible issue could be a small leak of coolant into the exhaust. I think you're going to have to have your engine connected up to a computer to monitor how well it's running or just accept replacing the cats.

 

@Dr_Al , You mention injectors, and this is in the back of my mind, THE potential culprit. I've kept up on plugs, and they've never looked bad or suspect, and I've never lost coolant. The tail pipe has always seemed to be sooty and black from day 1. Can anyone give me direction walking into service (preferably a Toyota dealership) and ask them to run/test diagnostics with specific things to look for? My suspicion is that the root cause is going to be obscure and difficult to diagnose, and some direction for the service team might be helpful.

 

BTW, I just completed my order for the last DS Magnaflow cat in stock at CarID at a mere $897. Ugh.... What the heck is causing these to fail on my truck???? I'm sure it isn't the cats.

 

honestly no matter the brand, i've been lucky to get 3 years out of aftermarket cats.. they just dont have the cell count of the OEM cats and go bad quick...

my 01 taco had 21k on its magnaflow cat when it started tossing me the p0420. and magnaflow is the ones i've had last longest

 

My buddy replaced his clunking passenger side cat last year with walker branded oem style cat no issues. Performs flawlessly.

Walker Exhaust Ultra EPA 54723...

 

Does your truck consume a lot of oil?

 

Damn, @Casper421 beat me to it... lol... on the oil consumption, or possibly oil leaking into the combustion chamber. This claimed my cat on my other car. A misfire started cooking my other car's cats, but it's been down for a while for maintenance.

 

@Casper421 and @blackdemon_tt , the truck really doesn't consume oil. I've always used Castrol 0W-20 full synthetic with one quart of Lucas full synthetic oil stabilizer and ussually kept 7,500 mile change intervals. I'm changing oil tonight at 10,000 miles (several long drives on this oil change so I took it farther than usual) and I'll check the dip stick level to see exactly if it is anything less than full before draining.

I really like the looks of the Walker cats mandrel bent tubes, and I REALLY like the price over the Magnaflows. I believe I would have gone this route but the Magnaflow is already on the way, last one in stock last night at CarID. I will say that when the Magnaflow DS was on back order a few years back but the PS came in, I was going to go with Eaton (I believe was the name) until I received them and compared them to the Magnaflows. The Eatons had crushed bends in the tubes and looked extremely restricting so I sent them back and waited out the back order. I did see a solid 3/4 increase in MPG with the Magnaflows, which over time paid for themselves- at that time they were about $350.

@empty_lord , you are probably right on the life of the aftermarket vs. OEM but the price on OEM is so much more painful and they can fail too. I'm thinking Walker on the next go-around if it comes up again. The PS Magnaflow has somewhere around 200K miles and no issues, so I'm still thinking there's something going on upstream causing the DS cat to fail.

 

@Casper421 and @blackdemon_tt , I just finished the oil change and checked the level before draining it. Found it to be 1/2 quart under full which means it lost 1/2 quart in 9,500 miles which I don't think is too bad for 371,000 miles.

I'm going to closely go over the exhaust ahead of the cats and see if I can find any exhaust leaks before I swap in the new one. There's got to be something going on for three cats to have failed on the DS and none on th PS over this many miles.

 

I think 1/2 a quart is actually normal. Obviously over time it may cause damage to the 'cc'. My Celica had oil icing on the exhaust short of the 'cc'. It failed, because it clogged it therefore wouldn't pass smog. Now your situation may be different. I would assume you may be having a misfire, or as stated before a fuel leak on bank 1 with excess fuel going into the cat therefore overheating and cooking that one cat. I would try to keep a close eye on temperature readings on bank 1's cat. If you have an OBD2 reader with the capability to read 'cc' temps, I would watch the 'cc' temps especially with towing.

 

Do you have techstream? If you do you can monitor the cat temp and see if there is a difference between left and right. You can also see the fuel trims to see if fuel is being added. How did the plugs look when you removed them? Are they the same left and right? You can use a temp gun to check the temperatures of the cats to see if one is running warmer than the other. It is possible that the failure is from the aftermarket cat and has nothing to do with the truck. I know this is not a fix and I personally wouldn't do it but there are devices you can buy to trick the ecm in thinking the cats are still on the truck. I understand that the Toyota cats are extremely expensive but maybe you will get lucky and someone will steal your cats and you can have insurance buy you new OEM ones. LOL.

 

I am no expert although I have enjoyed reading these forums, since you asked why the left cat keeps failing, I would like to let you know my opinion. The fuel rails in the Tundra are run in series, first it feeds the left side, then the right side, then the fuel pressure regulator decides how much fuel to allow back to the tank. This causes left side to have slightly higher fuel pressure so it receives a little more fuel than the right side. Normally, this is no big deal. When you run full throttle the engine is in 'open loop' running rich and the fuel pressure differential is higher causing the left side to run even richer than the right side. Doing this for an extended amount of time is pretty hard on the cats, especially the left one. Aftermarket cats are not as durable as OEM.

That is my thought as to why you are about to put another new cat on the left side.

Some (supercharged) have converted the fuel system to a parallel configuration so that (in theory) the right and left banks have identical fuel pressure under all conditions.