I have a 2007 Prius catalytic converter died a couple months ago, DTC code 0420 and running totally clogged car will only run at slow speeds. Shortly after the problem I bought a cheap OBDII scanner and noticed that I had DTC codes 2237 and 2238, indicating an air/fuel sensor problem and probably a very rich running engine. I may have resolved that, the connector needed unplugging then replugging at which point the codes disappeared. But just recently I was finally able to remove the exhaust pipe (manifold to muffler) which has the catalytic converter and two resonators in it, I looked inside the manifold end (catalytic converter) and at first I thought everything had melted, but no when I looked harder I saw that it appeared to be glazed over with a few small pinholes where I could see into the honeycomb of the catalytic converter. So I was able to easily scrape off this thin "glazed" layer, and the entire honeycomb appeared, reasonably intact after all these years. Time for the guitar-string test! A guitar string passed easily through many of the honeycomb cells and all the way through the catalytic converter. No internal damage noted. So what could cause such a glazing? The car had run for a few hundred miles with the air/fuel sensor problem P2237/P2238, but also this is a fairly old and well used Prius with about 400,000 miles on it, in the last few years the ICE has used a lot of oil (valve stem leaks). Do we think that the oil use or the air/fuel sensor rich running problem could have caused this glazing? Thanks! Lee McGee Fiddletown, California
Got it, so I guess I am going to have to make this a normal maintenance thing and scrape clean my catalytic converter every 100,000 miles or so. 500,000 600,000 700,000
I wouldn't scrape them. Typically, those honeycombs are fragile. Maybe not oranges to oranges, yet look to Ferrari model 360 ingesting honeycombs for expensive "horror" stories. Although your decision. Good luck.
Only a Ferrari 360 can do that. A Prius with 600,000 miles on it should be fine. The ICE does not have that much horsepower.
Burning oil is the most common cause of cats going bad on high mileage Prii. The Prius' ECU is quite good at keeping the air fuel ratio right around stoichiometric, so rich running usually isn't the problem. If you google around, you can find methods of soaking the cat in different chemicals which can keep the cat working as expected longer. However if you're burning oil, you're not really solving the problem. The working theory on why high mileage Prii burn oil is that the piston rings wear and also get gunked up by hydrocarbons. This allows more blow by than normal, which results in additional pressure in the crankcase, which then pushes oil vapors through the PCV to be burned by the engine. There are two things you can do to help: 1. Run a few tanks of a high quality engine/fuel injector cleaner gas additive (Techron or other with PEA). Some users report reduced oil use, some not. 2. Install an oil catch can. This won't stop oil use, but will catch a lot of it from burning in the engine, helping save the cat. You'll want to solve the A/F ratio sensor problem. It may be it just has a layer of crud on it as well, and pulling it out and cleaning may clear the code.
Option 3. Is piston soak method. You just pour the cleaner into the cylinder from spark plug hole and let it seep through the piston rings into the oil pan then change the oil and get the excess cleaner out of the cylinders. If you decide to go with catch can don’t forget to empty it! In some driving conditions you might have to do it in every couple of days (especially short trips in cold temperature). And in cold catch can can freeze. The way Toyota installed the air-fuel ratio sensor it might be impossible to remove it without breaking it so cleaning it might not be an option.
Amen brother! My 2008 burns a lot of oil and (at 175K miles) the cat clogged so badly that it failed the smog test, even after lowering into a vat of acid for 6 hours. So I replaced it (US$ 1,800) and promised myself that I would get the engine rebuilt to avoid clogging another cat. So, here I am, 37k miles later, and I'm starting to get catalytic errors. This is what the plugs look like after 37K miles: This time I learned about the marvel Mystery oil soak and the catch can! I have the cylinders soaking now and will install a catch can in both of my Prii. If that doesn't work, then I will really have to consider a rebuild... and a quasi legal cat replacement. (it's ... complicated in California, pm me for details)
What weight oil are you using? Doesn't look like you're using NGK IFR5A11 (or Denso SK16R11) plugs, what model # NGK plugs are you using?
Those spark plugs are excessive worn! They should have being replaced long time ago. You can see some kind of caking on the plugs, as a result of oil burning. Get that engine rebuilt, to stop the oil leaks, or you risks getting the catalyst destroyed again.
I have 430,000 miles on the Prius now, the cat converter glazing was cleaned easily with a knife by removing the exhaust, was only glazed at the engine connect end of the exhaust, no problems internally so no need to worry about the health issues! There is no check engine light or problems at all currently. Except that the car was totalled about 2 years ago from a rear end collision, no more room for the standard yellow top 12v battery, I'm using a much smaller 12v battery instead, which works just fine! The Prius does not seem to care. I hope to see 500,000 miles on it some day. The car is just used locally in my rural area here, it does not get all that many miles these days, might take many more years to get to 500,000. 2007 Prius Gen 2. Cheers, Lee
I wonder....: would Oxi-Clean solution soaks work on a Catalytic Converter? Is it all stainless steel and/or other non-corrosive metals? Oxi is a moderately strong caustic, not quite as strong as Oven Cleaner. It will react with regular steel, aluminum, you'd want to avoid this. With the 3rd gens there's a Exhaust Gas Recirculation "cooler", basically a passage with a rectangular cross section, with a small radiator coolant labyrinth, that get's carbonned up. Mixing an Oxi-Clean solution, hot tap water and as saturated as possible, pouring it and letting it soak, it reacts with the carbon, floats it off. It takes maybe 1/2 dozen hour long soaks and rinses to get it clean, very clean.
The ones in the photo are ngk bkr5eix-11 I didn't think to double check when the guy at the parts store handed them to me. The new ones are Denso SK16R11
