Catalytic converter

Hey all, new tundra owner here. Im needing to replace my exhaust system(muffler and pipes rusted beyond repair). My downstream o2 sensor connections seem to be welded over(previous owner). So I’m leaning towards just replacing the catalytic converters as well. I’ve noticed a decline in power and gas mileage(not to mention CEL) and the exhaust pipe just after the cats is cold even after running the truck at operating temp, leading me to believe the cats are clogged.

can anyone confirm these are OEM catalytic converters? I can’t find a part number or brand name. I put my hand up for size comparison (the cats are smaller than what I would expect from OEM)

if anyone has experience with aftermarket cats I’d love your input.

 

Those are the OEM catalytic converters. They sell them as part of the exhaust pipe section and they typically go for $2k each. Best to confirm if they’re bad before replacing. Aftermarket CATs are never as good and you need to buy CARB compliant ones if you don’t want to take a chance on them throwing a CEL.

I’d unweld the sensors and swap to see if the fault tracks to determine if it’s the O2 sensor. 99% of the time it’s the downstream O2 sensor causing the fault. They may be partially clogged but not enough to buy new ones. Some have cut theirs out and soaked them overnight to clean them before reinstalling.

 

This, totally. Two huge, critical takeaways there, esp. the latter, knowing how problematic aftermarket is. Walker, Summit Racing's store brand, Magnaflow are the three brands folks have had luck with in these trucks.

Though I'd add: The upstream sensors are what help the ECU set fuel/air ratio, fuel trims. So if you have the added system of bogging down, that signals to me it's the upstream. I encourage you to READ THIS before you touch anything.

Tons of other info for you about your truck, seeing this is your 1s post, over here: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

It'd help us help you if we knew what codes you're throwing. And if you ever replaced the fuel filter, that would be helpful to know also, OEM has a far less restrictive fuel filter than other companies, by design. Factory will last 15+ years with no problem, aftermarket often crap out/clog within a year. The OEM just doesn't catch as much, and that's EXACTLY how Toyota wants/expect it to be for the engine they designed. So much so, they deleted the inline fuel filter totally for 2005-2006 models.

 

Thanks for the replies everyone. I’m going to try to clean the cats first and weld a new bung for the downstream o2 sensors. I’ve got the upstream o2 sensors on the way because one cord looks chewed on so I’m just going to replace both. I’ve had good luck with denso in the past and I’ve heard they’re the manufacturer for these tundras anyway(correct me if I’m wrong).
I can’t remember the codes off hand, I’ll read them again.
I’ll replace the fuel filter at the same time I do all of this.
I know the upstream o2 sensor is primarily responsible for fuel mixture, and I always assumed the downstream sensors only function was to report catalytic converter function. However I’ve read that they also play a role in the fuel trim/air-fuel ratio. Is this correct? This would be surprising to me.

 

I don’t know where you got your upstream O2 sensors but Rockauto.com sells Denso cheap and they aren’t knock offs. Many here have used them as a source.

I don’t know how much the downstream sensors impact the air/fuel ratio. Common sense tells me it’s minimal if at all.

 

Cat cleaner is a bit of a sham in my experience. On these trucks, the factory cats typically DO NOT fail unless you did something really stupid, like Seafoam'd the top-end of the truck a couple of times per year, or let it run rich or lean for years on end.

Denso is the OEM, and as long as you don't buy them on scAmazon, fleaBay, Wallyworld or similar marketplaces, you don't need to worry about getting counterfeits. As long as you're careful to look up the 'EXACT FIT' parts at www.densoautoparts.com you should be golden. Never want to buy their 'universal' part, cutting OEM harnesses is a huge mistake. I know it may sound cliche, but DO NOT trust any of the websites I just mentioned for auto/small engine/appliance parts. It is rife with fakes. Probably spark plugs are the most egregious.

That fuel filter, it's almost never the fuel filter, but ... the fuel filter is typically not a problem. Toyota does recommend periodic replacement, but we've seen all of one time out fo hundreds where it was the actual problem ... and when the person pulled the filter, it was an aftermarket filter. You have guys on here with 300k-400k miles still rocking the factory filter, no problem. Anyway, be ready for cussing getting the bolts loose, hit em with Kroil or PB now, and expect to get gas in the face, and bust some knuckles replacing it.

Function of upstream/downstream filters for these trucks is in my "READ THIS" link above. Primary role is enabling ECU delta.