Hi,
I have a 2009 Sienna with 223K 3.5 V6 auto that has been throwing the P0420 for more than a year. In the last 6 months it has started occasionally throwing a P0300 (and P0301, etc) and runs so poorly I have to pull over and shut it off for a few minutes. The misfire code seems to happen when it's run pretty hard for a while. It's fine after restarting it. I've replace the O2 sensors, cleaned the MAP sensor, etc. checked for vacuum leaks... Ran some seafoam thru the intake, etc. It seems like the Cat is the culprit here or is there anything else I can try? Could the two issues be related? Could the coil packs be causing some of the problem?
And finally, is it possible to replace the exhaust manifold and Cat (I believe it comes a one piece) on bank one (rear) without a lift (jackstands only) at home? Probably need to replace the plugs as well.
Thanks!
The two issues are probably most definitely related. Scotty has a video about this and my bet is on it being a clogged catalytic converter especially since you've already replaced the O2 sensors. The downstream O2 sensor is in charge of determining if the catalytic converter is clogged. The upstream O2 sensor reads how much exhaust is being pushed through the manifold. The upstream O2 sensor tells the engine when to retard the timing etc and if the readings at that sensor are messed up because of a clogged catalytic converter a car could misfire as a result. I would get a new cat.
@inthedetails
Hi, Thanks for your reply. I'm going to try to check the cat over the weekend. I'm wondering if the replacement is something I can pull off myself without a lift.
Why did you use sea foam? It can destroy cat.
check out the back pressure of the cat to see if it is clogged or not.
if clogged, follow scotty’s video on how to clean cat.
@yaser
Thanks. The CEL has been on for a while and I figured if it's already bad I don't have too much to lose. I watched the video and will try to check it over the weekend. Thanks again.