Catalytic Converter

[DMC88]

I was wondering if it was possible to have a bad cat with no p0403 code or any code that indicates a bad cat. I've been throwing p0171 and p0306 for about a month and haven't been able to fix it. I put new denso af and o2 sensors in about 7 months ago, a new denso maf sensor in last weekend, new plugs on bank 1, new pcv valve, I've checked for vacuum leaks pretty much across the whole engine, and within 50 miles or so the new plugs were completely black. I pulled both sensors on bank 1 and they too were black. I've tried everything I can think of and nothing has fixed the problem, which really has me leaning towards a bad cat, but its not giving me the code for it. I would think a fuel pressure problem would affect both banks and I doubt all 3 injectors would act up simultaneously on only one bank. I bought a scan tool, and bank 1 is running high on the fuel trims. The freeze frame shows the ltft for bank 1 at 2.3%, but while I was watching it driving down the road it was pretty consistent at 29.7%. I've researched this for the past month, and have tried everything I could find. The only other thing I could think of would be a bad cat, but the fact there's no code for it has me doubting it. Any suggestions on what else ot might be? I need this running right and its driving me crazy trying to figure it out! If I were to take it off to look at it would I be able to tell if it was bad?

 

[Jerry101]

Thanks for "bumping" this thread up to July 2021. If you are inclined, I would be interested in your newest findings and conclusions. And if others have found the best solution to keep our "cats" from being stolen, it would be appreciated.

 

[DMC88]

If I could have started a new thread I would have, but I dont have enough posts so it wouldn't let me

 

[DMC88]

Thanks guys...

 

[Ali0227]

Possible bad cat, 04 runner won’t go beyond 2500 rpms

Oxygen sensors may begin to lose their efficiency after 100k miles. My T4R was well over the 100k mark so that is why I decided to replace the sensors first. Catalytic converters usually go bad from low RPM and infrequent use. I drive mine daily and usually on the highway, minimizing the possibility of cat failure.

Thanks for person mentioning cats go bad from infrequent use. I stored my vehicle for 9 months and it won’t go over 2500 rpms even going 80 on the highway. I thought the idle was running a little slow in park and stopped at lights.

Car in mechanic’s shop now, will be a bummer if I have to replace both cats! Anyone know if they both go bad or is it often just one?

 

[JQUICK]

Thanks! But I saw somewhere that if you smell a sulfur smell it means the cat is bad. And I smell it only when I gas it good to go up a hill or when getting on the highway. Normal driving around town and I never smell it. I bought sensors, four of them, but quickly saw it is near impossible to replace them without putting the 4Runner up in the air and removing the Cat. I can't see how people get their hands in there for these sensors. I bought the funny looking wrench for the job but I can't break those old sensors loose.

That is the MOST common cause. There have been many catalytic converters replaced when in reality it was just an O2 sensor. The ECU throws a code that makes it seem like the cat is bad. But all that means is the the down stream O2 sensors is not sending the ECU a good signal. This can either be a bad cat...OR a bad O2. A good mechanic will then have to run further tests to determine what the actual cause is.

Believe it or not...it's rare for a cat to go bad. They should last the life of the vehicle.