Burned out my catalytic converters?

I had some really bad misfiring caused by a failed spark plug thread in cylinder 5. Had to get the truck towed. Took to the mechanic and got a new thread, plug and coil and she seems to be running pretty well but I'm now getting a p0420 code. Is it reasonable to assume the misfiring events/rough running burned out a Cat?

 

No, that's the last thing to try, since it's the most expensive. Could need plugs, wire, have a vacuum leak, exhaust leak, O2 sensor issue...plus some other stuff that slips my mind at the moment. Lots to test and try before you go after the cat

 

Yes absolutely. Converters do not like raw fuel, it lights them off like a jack-o-lantern

That's why the check engine light will flash during a misfire situation. The manufacturer is trying to get your attention to stop driving before the cat is damaged. If the converter fails in less than 8 yrs/80k miles they have to warranty it..

 

It all depends Just how long and how many miles .

I have seen one cylinder not firing for months not causing and problem.

Pop out the rear sensor clean it off try again.

Look for leaking exhaust gaskets between cats.

 

I had the misfiring begin on a Friday with a fair amount of jerking leading up to the engine making a bunch of slapping noises from misfiring on a Saturday night. Probably drove it around 100 miles during those two days. The check engine light briefly flashed before I pulled over. Unfortunately I had to drive it like that for about ten minutes due to highway construction.

 

I’ve had the rear O2 sensor replaced (denso). I also had the exhaust repaired between the Cat and muffler. Still getting a P0420 code. Runs smooth and idles about perfectly at ~700 rpm’s. Has a slight jostling at idle but the needle doesn’t move. Might be paranoid at this point. Fuel mileage is good at 19-20 mpg. No other codes.

i know I still have a small exhaust leak between the exhaust manifold and the first cat and behind the second cat from a bad weld. The exhaust mechanic said the pinhole type leaks are insignificant (shouldn’t cause a p0420 code) that he couldn’t identify any leak just listening or feeling for it. I showed him my pictures where I used a vacuum to push air from the exhaust towards the engine and soapy water to identify the leaks. He basically shrugged his shoulders. Should I demand my money back given they aren’t willing to get it perfectly sealed? I mean, I feel like I shouldn’t be having any leaks.

So what should my next step be? Replace the air fuel sensor? Replace the exhaust manifold gasket? Assume it is the cat? Assume it is still from these small leaks?

 

Fix the leaks… the front 02 sensor IS that sensitive.

 

Agreed. Any obvious air leaks cannot be ignored if you have a pesky p0420 that keeps returning

 

Agreed as well. Those appear to be some significant leaks given the amount of bubbles, especially right around the 1 sensor. The P0420 code, from my understanding, pops due to the differentiation of Sensor 2 numbers compared to Sensor 1 numbers being too far out of whack, so if Sensor 1 numbers are skewed (reading leaner than actual) due to those air leaks it makes it seem like the cat isn't doing its job efficiently enough because Sensor 2 is showing much more rich in comparison.

 

I'd give the first guy a chance. Ask him to seal it up. If he says it's fine, get a second opinion from another shop. If the second opinion is "seal it up" then you can either pay the second shop to do the work, or give the first shop another chance to fix their work... If they opt not to, then it's time for an honest yelp/google review about the situation.

 

Might have luck with some of that exhaust sealant putty..

 

Can anyone tell me anything based off of these numbers? Fuel trims look ok I think? Why N/A for the O2 bank 1 Sensor 2? I just replaced the rear O2 sensor.

 

Bank 1 sensor 1 should be a quasi saw tooth pattern, bank 1 sensor 2, after the cat, should be a relatively smooth line with some smooth wave transistions.

 

Just wanted to close this thread out by noting my issue was an exhaust leak. Finally took my truck to the right muffler guy and he sealed up a bad weld between the rear cat and rear O2 sensor. 600 miles later and the 420 code has stayed away.

 

Hoping this could be the case for me. But I also have 300k on these cats. What’s your mileage?

 

250,000 miles. Have you tested for leaks?

Also, around 245,000 miles I had a spark plug give out and I drove for about 10 minutes at highway speed misfiring big time. So my cats took quite a load of fuel and appear to have handled it just fine. Just something to note.