2008 V6 Camry

2008 Toyota Camry V6 Automatic. 317K miles Regularly maintained by me, Oil changes by my dad every 5K miles. Does not burn oil at all.
Great car has alway ran great untill last year.

I keep getting Error code P0420 - or Catalyst System Efficiency Below Threshold (Bank 1)
80% of the time the car runs fine with this code, but maybe 3-4 time a month it will stummble to the point were you want to pull over then like a switch it will be back to normal. WTF
So far I have changed (All the spark plugs-Coils- Both PRE CAT O2 sensors.) This weekend I changed the downstreem (after Cat O2) on Bank1.

My dad said it drove great this morning and was a LITTE better however on the way home the Check engine light came on and ran kinda rough.
So this weekend I will change the last O2 sensor after the cat on bank 2 and see if that helps.

Whats next if that doesnt work? It doesnt seam like a plugged Cat and @317K plus miles I'd hate to waste the money, Is there somthing else that could be giving me this code?


Thanks for any input and the Mods can Move this if I'm in the wrong place.

 

Can you get the fuel system "smoked"?

You could have a bad vacuum hose leaking.

 

It's a worn cat, not a plugged cat.

95% of the time P0420 is a worn cat and needs to be replaced. P0420 actually signifies the sensors are working. Typically only an exhaust leak or worn cat can trigger it.

 

If there are no exhaust leaks upstream or near the O2 sensors the P0420 is 99% of the time a failed Cat, that code itself will not cause a driveabilty problem though.

Now if the converter is coming apart (usually they will rattle like a marbles in a tin can when this happens) it can intermittently plug up the exhaust and cause the symptoms you describe.

 

Does that car have rear cat?

 

Zero exhaust leaks, The transmission has been rebuilt,shifts fine and no weird noises.
I was kinda leaning towards the Cat as well but wasnt sure how a bad cat can be so intermittent. We dont have to Smog the car where we live so I guess we can go with a cheap Amazon Cat.

I just hate to throw parts at it.

 

I dont think It does. I only saw 2 one on each exhaust manifold.

 

I want to be clear, the cat code is not the cause of your drivability problem. Now if the cat is plugged or coming apart it could cause your issue, an exhaust backpressure test would tell you if it's plugged/restricted or not.

If it's not then you most likely have a problem unrelated to the cat.

 

Start replacing all those dry rotted vacuum hoses

 

(If it's not then you most likely have a problem unrelated to the cat) I dont like this!! ha ha. It's always the P0420 code I clear it and it comes back. You might be right.

Im looking into what else can throw this code cause I've done just about everything I can, Im thinking the Cat is next.
I'll be looking at the car next weekend and Ill check Vaccum lines and loose stuff. It's my dads car and hes drives it 135 miles a day.

Thank you guys for the suggestions And I will keep this updated as I go till the end in the hope that it might help somone down the road.

 

I've never seen a cat code cause a drivability problem, they are almost always the result of a failed cat (which itself can either be due to high mileage or the result of another problem like a misfire that was left unchecked).

As far as drivability unless it is coming apart (rattling), converters are either restricted/plugged or they aren't. In either case a plugged one typically shows up as a severe lack of power.

That's about all I can tell you without seeing it myself or you doing some testing and collecting some scan data when the problem is occurring.

 

I told my dad if hes driving through town and it starts running like shit, pull into the local shop leave it running so they can plug into it and look at it in real time to pin point the isseue.

 

Yea it would help to be able to see scan data when it's acting up if you know what to look for.

 

I've been driving with p0420 and p0430 for 3 years straight on my beater smells bad, dont care.

 

So 320k miles
Replaced all plugs all coils all O2 sensors,
Still have the P0420 code. The car runs rough at 1500-2000 Rpm in park and driving it shakes really bad at those rpm's.
I floor it it takes off like a bat out of hell but with the shaking.
It is worse after the car warms up

Should we look into replacing the cat?

 

No smog test, straight pipe that baby, remove cat and res to a nice muffler, you’ll be good to go. Might get the code but the car will have some fresh flow

To be honest though it sounds a little more than a bad cat, especially with it running rough at that rpm. Almost sounds like a fuel to air ratio issue. I’d lean towards a bad coil but you stated you’ve changed them all. The shaking part is what has me thinking.

 

I don't see that Ramona (zip 92065) is exempt from smog checks. Are you out by Santa Ysabel? At the very least, it will be a change-of-ownership smog check - and the seller is responsible for the smog check.

I think you may have a cat built into each exhaust manifold, plus the one(s) in the exhaust tubing.

 

I live in Ramona and my parents live in Julian.
Julian doesn't require smog. If we sell the car,then yes smog would be required. My truck is registered in Julian also.

The exhaust manifold on the camry has the cat built onto it like this picture..

 

Maybe an injector? But would that throw a Cat code? I'm not sure.

 

Read this after doing a bit of good ole “googling” and figured I’d post it. This entire thread spoke about exactly what you are speaking of and a bad cat seemed to be their culprit, after basically trying everything else. I believe theirs was in a corolla around your year Camry. Not saying it is a bad cat but may have a good chance at being your issue.