P0420 catalytic code

2003 Tacoma 3.4.
Was running rough so shop did tests and replaced following.
Maf sensor
Pre cat O2
Spark plugs
Fuel filter
Fuel pump.
Cleaned throttle body
Truck runs good. Fuel milage is poor. When driving around the code for carylitic efficiency comes on once in a while. Tuck has 190k miles. I am wondering if these cats normally fail. We have no smog tests here. Should I cut it out? Thanks

 

I'm currently having the same problem with my truck, try running some mid grade fuel instead of the regular in it. Or if available in your area some non ethanol fuel. I think it has something to do with the air/fuel ratio with the bad ethanol gas these days. I'm replacing the front o2 sensor this weekend to see if that helps mine. Mine is kind of bipolar. Another route to go is a o2 simulater from URD Racings website that tricks the front o2 sensor saying that your air/fuel ratio in your exhaust is good. I hope any of this helps. Merry Christmas!

 

The other day my truck stalled on start up. I may try urd but I would like to fix properly first. I have read that removing rhe cats sounds horrible. Most say it's the main cat that fails causing this. Is this truck?

 

I only have a single cat. I took mine out to inspect it visually and it wasn't clogged or anything, and I'm getting good flow so I don't think it has anything to do with the cat. I wouldn't recommend taking yours out, my buddy did on his Nissan and it was obnoxiously loud and it sounded terrible. But some people like that. I've been dealing with this for about 6 months. Have you used injector cleaner recently by any chance?

 

Also I almost seem to hear a little exhaust leak when come start.

 

Just ran injector cleaner yesterday. Lucas. I wonder if I could take mine off, cut it open and inept then re weld

 

Mine started happening after I ran a bottle of Lucas injector cleaner through my truck... Just saying haha. Mine also seems like it has a exhaust leak upon start up but goes away after it warms up. Sounds like it's coming off the collector.

 

I have read that catalytic failure accures when there is a fueling issue which I had with my truck (previous owner did) so he replaced all that stuff. Maybe I should pop my cat off and attempt to clean?

 

How do you go about doing that? Brakleen it out?

 

I'm not to sure lol I sounds if I could pull it off. Cut it open and clean all the carbon and weld back together

 

Probably be easier to just get a magnaflow high flow cat or something along those lines. Maybe the injector cleaner is clogging up the cat or something. It seems weird that it happened after you used it same as me.

 

No kidding my milage is bad. I hav only got 100 miles to half a tank. Mind you it is winter and that is town driving. 33 tires. 3.4 5 speed

 

My truck is in kilos so I usually get about 210 to a half a tank. I'm not sure how many miles that is. But 200 miles per tank seems pretty low. How many miles on the truck? Have you regeared or stock gearing?

 

I'm in km to. I will get about just under 200 km on half tank town driving only

 

Stock. 310km

 

Maybe gearing has something to do with bad mileage. along with the bad winter fuel. My truck has 536,xxx kilos in it btw

 

Gearing stock? Yeah winter fuel doesn't help.

 

I wrote a whole article about this:

https://www.tacomaworld.com/threads/addressing-some-common-misnomers-of-the-p0420-code.396763/

Please comment if it helps.

 

Ill just say that your catalytic has no bearing on your fuel economy. It sounds like your mechanic just did a tune up. Most of the owners on here are their own mechanics, so telling you something to tell your guy really isnt going to be helpful. Id do a through engine cleaning with seafoam, these trucks are known for pulling a lot of oil through the engine. There is no way to tell what he cleaned when he said he cleaned the throttle body.

 

I am fairly mechanically inclined and know the mechanic who performed all the work. I also have another Tacoma (98) so I am very familiar with these trucks. Never really had any catalytic issues before.