Alternative P0420 catalyst fix...

Jarpin

Jarpin

Joined
Feb 25, 2009
Messages
322
Location
TX
Some people are against the idea of using anything in the fuel tank to possibly clean the PM bits in the Cat. The infamous 1 gallon Lacquer thinner method or Cataclean®. Some of those people within that think tank suggest hard acceleration at WOT to help the exhaust reach a hotter temp to burn off any impurities in the Cat.

(Keeping the previous method in mind) I know this sounds a little risky, but what about having the engine running at normal operating temperature and then just heating the cat a little more with a propane torch for perhaps 5 minutes or so? Would this achieve a similar effect without the danger of a car accident from higher speeds? Thanks.
 
Back when I had a car that gave P0420 codes, I found that spraying carb or throttle body cleaner into the throttle with the engine running, using maybe 1/4 to 1/2 a can, would make the P0420 code stay away for 10,000 to 15,000 miles...
 
ctechbob said:
I doubt you would be able to evenly heat the cat for long enough to make much of a difference.
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This. Plus I'm thinking you'll start melting/deforming the exterior sheetmetal before getting any significant heat to the catalyst. Think of the exterior as a heat shield (and in fact many cats are wrapped in a secondary external heat shield) for the purposes of what OP proposes.

Non-foulers are the only definitive fix I've found, and only on certain makes.
 
Also....just thinking out loud as a metalworker-type.....if you were going to attempt this (and I still don't think it'll work) you'd want a huge O/A torch with a huge rosebud. You want LOTS of heat spread out over a relatively large area so a big rosebud moving around the entire length of the cat. You need big tanks to not exceed the 1/7 (old) 1/10 (new) rule.

A little handheld LP or MAPP gas torch will just waste time and $ with no results IMO.
 
If you run hard under a load it can reach towards 1000F inside the cat. Not sure how your going to get it much hotter with an external torch.

Are you trying to actually fix it, or make it through a test cycle? I have heard Cataclean will get you for a few days, but it always comes back.

I personally don't see how something that goes through your combustion chamber can still possibly have enough of whatever it is left to clean much of anything more than a bit. If I "had" to fix a cat - because I couldn't find or afford a new one or whatever, I would try removing it and soaking it in something for a few days?
 
Had a P0420 on our 2004 RX330 at 253k (mid 2020) and the independent repair shop was ready to replace the converter.

Instead, I ran a bottle of Cataclean, shell premium and passed Colorado emissions with the fast pass a few weeks later. The light came back on at 265k, ran another bottle cleared code and passed emissions again in 2022. Was good until recently, when the CEL came on again at 280k. (lather, rinse, repeat)

Three bottles of Cataclean is still much cheaper than the $1500 catalytic converter quote.
 
newtoncd8 said:
Had a P0420 on our 2004 RX330 at 253k (mid 2020) and the independent repair shop was ready to replace the converter.

Instead, I ran a bottle of Cataclean, shell premium and passed Colorado emissions with the fast pass a few weeks later. The light came back on at 265k, ran another bottle cleared code and passed emissions again in 2022. Was good until recently, when the CEL came on again at 280k. (lather, rinse, repeat)

Three bottles of Cataclean is still much cheaper than the $1500 catalytic converter quote.
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I'm going to try this, but with the Dura Lube catalyst cleaner and premium gas. Sounds like it's worth a try without even thinking about the downstream sensor at this point.
 
Jarpin said:
No emissions county....but I'm terrified if there's a possibility of the CAT being coolant fouled due to a Head Gasket issue.
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As I recall that also tends to foul out the oxygen sensors too. It's the silicates in coolant that does it, so if your vehicle is running a silicate-free coolant like Dexcool, theoretically it wouldn't damage the cat.
 
Jarpin said:
No emissions county....but I'm terrified if there's a possibility of the CAT being coolant fouled due to a Head Gasket issue.
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That's a separate problem. Sounds like head gasket sealer would be more useful than cataclean :unsure:

I can vouch for Bar's Leaks HG-1 head gasket sealer. Another good one is Blue Devil Pour-N-Go
 
Jarpin said:
Has anyone tried spraying brake parts cleaner into the upstream sensor opening toward the CAT to see if it can clean off the inside surfaces?
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If you're that desperate maybe try the Seafoam thing you're supposed to run through the throttle body at increased idle

But if you're that desperate why not try non-foulers first? Do you believe the cat is ACTUALLY significantly clogged or you just want the CEL to go away?
 
Are you convinced it's one of the cats? If the vehicle throwing the code hasn't had a problem with excessive oil burning or coolant leak, etc., could it be one of the O2 sensors? Especially if it's a high mileage vehicle. They seem to last longer than they did decades ago but they all eventually go. Some years ago, I had everyone tell me that I needed a primary cat. I was lucky and two new O2 sensors solved the problem for many more years.
 
D60 said:
If you're that desperate maybe try the Seafoam thing you're supposed to run through the throttle body at increased idle

But if you're that desperate why not try non-foulers first? Do you believe the cat is ACTUALLY significantly clogged or you just want the CEL to go away?
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Hey D60. I have been using Costco top tier 87 gas for over 3 years now perhaps QT also on occasion. I want the light to go away, but I want it to go away correctly without the use of a bung device or the thousand or so for a new CAT. I just dumped in the Dura-Lube severe catalyst/exhaust cleaner along with a full tank of premium 93. let's see if that helps. If it doesn't, I'm getting a refund and using that toward the purchase of a new downstream sensor. Seafoam might also be used.
 
hank2 said:
Are you convinced it's one of the cats? If the vehicle throwing the code hasn't had a problem with excessive oil burning or coolant leak, etc., could it be one of the O2 sensors? Especially if it's a high mileage vehicle. They seem to last longer than they did decades ago but they all eventually go. Some years ago, I had everyone tell me that I needed a primary cat. I was lucky and two new O2 sensors solved the problem for many more years.
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Yessir....I was thinking exactly that. The next step is to pull the sensor and check resistance across the heater wires for proper ohms, and also blow torch the probe end to see if it is generating the voltage requirement for the ECU. The only thing that made me dismiss this idea is that I just replaced the downstream sensor two years ago, I guess it could have failed prematurely...
 
On a older 2.5L Subaru with a very persistent po420 code... Hint: Anti-Fouler and to this day it "passes" every year. Yeah the light comes back on if you use CC, but its a erase code, run for 60 miles and get a new sticker for the year. I would not do this on a new car but would fix the issue correctly... but a 200K mile Subaru - absolutely.
Final thought on Subarus a simple worn out exhaust gasket could give you a po420 code... But to fix said gasket you gotta go in deep to fix.... and cost to do so is substantial.
 
Jarpin said:
Has anyone tried spraying brake parts cleaner into the upstream sensor opening toward the CAT to see if it can clean off the inside surfaces?
Click to expand...
what u want achieve?
get rid of saps or antifreeze crud? that will not work.
you some kind of acid to etch it away. maybe hot citric acid could do. (it does, on limescale...)
 
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