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Catalytic P0420 easy “repair”

6.4K views 17 replies 12 participants last post by  pandrson  
#1 ·
I wanted to share what I’ve experienced as an effective solution for the catalytic converter issues with these aging models. I know there will likely be a bunch of naysayers who cite Scottie as a hack, but I thought this could help some who truly wants to try a low cost solution for these expensive parts. After doing this treatment, my P0420 P0430 codes went away and my engine gained significant power. I’ve done this on both my 2008 Ody and 2008 Pilot with very positive results.
Here is the process I used:
1. Run gas tank down to less than 1/2 full - closer to 1/3 full.
2. Pour in an entire gallon of lacquer thinner. You can buy these at Lowe’s for $21.
3. Good on a road trip and run the engine without stopping until it is very low on gas. As you get near the end of the tank, run it at high RPMs for extended times to get the Cat very hot and burn out the buildup. I would run mine around 5K RPMs for about 45 seconds, then back off a bit, and back up again, and did this about 20 times. Don’t overheat your engine, but get that baby cleaned out.

After doing this I haven’t got the codes in over 2 years. I hope this is helpful to others. Replacing these Cats is very expensive and very difficult to do, even for those who do their own mechanic work.
 
#2 ·
It's not a blanket P0420/30 repair.

It's important to understand that if the substrate itself in the converter is damaged (similar to what happens so often on 05-07 VCM Odys), no amount of "cleaning" is going to fix that.
 
owns 2006 Honda Odyssey EX
#3 · (Edited)
Melted cats cannot be cleaned or repaired. Some people beat them out and use O2 sensor defoulers, for downstream ones.

That's what I am going to to, when my cats die. IMO, it'll be much less risk, than using lacquer thinner and revving engine at 5K.. I have seen enough melted pistons.
 
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#4 ·
I would think you could try this to see if the lacquer thinner will work. If you get P0420 and when you clear it the code goes away and doesn't come back for a while. This could be hours, to months. The longer it stays off the less clogged it is.
If you get P0420 followed by O2 codes, or get a lot of O2 codes, that would be your cats falling apart.
Any thoughts on this?
 
#5 · (Edited)
I agree with Wiimaster. "It's not a blanket P0420/30 repair. "

The cleaners (including lacquer thinner and many other commercially available products) either work or don't work depend on what left of the filtrate ability for successful chemical reaction as exhaust gas passing thru the filtrate. If your CATs are worn down meaning there is not much chemical left in those CATs or some/all of filtrate inside are gone, it doesn't matter how much cleaners to push it thru. You are not going to revive those CATs.

The P0420(bank 1) or P0430 (bank 2) codes mean that your CATs are working less than 95% efficiency, and the Federal government wants you to replace them.

Can you imagine getting fired from your job because you are only capable of working at 94.5% efficiency?
 
#6 ·
Agree that Scotty not always making sense in his post and videos, but as an entry level DIYer, i do respect him as i learn so much from him during my early DIYing. so for his lacqure thinner trick,here is my own experience on my 06 Ody Exl, i had done the same, and my own conclusion is positive even there is no thoroughly theory to back it up.
Last summer, after P0300s misfire codes showing (only misfire code since owned this used van from 2018) I had learned from this forum how Honda VCM could damage this engine and the cats, and how the DIYer should do. I had VCM muted and plugs replaced, yeah, bank 1's 3 old plugs for sure weren't looking good, oil fouled; for the cats, luckily, i didn't got any P0420 or P0430 codes yet and the infra thermos gun showed okey data, but I can't stop thinking how long the Cat would hold up and i noticed there were some symptoms like hesitation, low power, so i decided to give a shot to Scotty trick as this is a low cost solution to my high mileage van and the web feedsback most are good. as shared by Scottn3, i did the same on a 300km round trip, felt no difference during driving, and I lowered gear into 3rd couple times under highway speed so engine boost the RPM over 3000 to increase temp even higher to burned out the residuals from previous VCM oil burning. almost to the bottom of tank after Gas light up, fill up with new fresh to dilute any leftover after back home. Power increase is noticable, no hesitation when accelerate from stop, might be own subjective feeling, but so far, engine running great and no feeling of intake exhaust breathing issue.
 
#7 · (Edited)
You can classify knowledge in three ways: There are things of which you know that you understand. There are things which you know that you do not understand. There are things of which you are not even aware that you do not understand. This third category is vast.

DTC codes related to the O2 sensors can be caused by failing O2 sensors, problematic fuel/air ratios or failing catalytic converters. Those discussing lacquer thinner are in this third category of knowledge. A qualified mechanic would be in the second category of knowledge and employ diagnostic procedures to identify underlying problems. He seeks to understand the cause of problems, not guess in the dark.

Lacquer thinner has different formulations depending on the manufacturer (and whether they have to meet VOC regulations), but you can assume that this fluid contains solvents that melt plastic. The fluid would also contain solvents such as acetone that clean fuel injectors (in addition to melting plastic). Those who say they noticed "increased power" after driving on lacquer thinner may have cleaned the fuel injectors using a harmful approach. By the time this fluid is combusted in the chamber, it (like all hydrocarbons) becomes carbon dioxide gas and water vapor.

Fix codes related to O2 sensors by troubleshooting the underlying causes, which could be a failing cat or something else. Don't listen to a buffoon yelling on youtube or posters saying "I tried it and it worked". They live in the third category of knowledge.
 
#11 ·
It's not that Cat cleaners or lacquer thinner don't work, but it is your Cat far too gone for them to work. You only have two options left--replacing your cat with a new one or manipulation (cheat).
 
#12 · (Edited)
I wanted to share what I’ve experienced as an effective solution for the catalytic converter issues with these aging models. I know there will likely be a bunch of naysayers who cite Scottie as a hack, but I thought this could help some who truly wants to try a low cost solution for these expensive parts. After doing this treatment, my P0420 P0430 codes went away and my engine gained significant power. I’ve done this on both my 2008 Ody and 2008 Pilot with very positive results.
Here is the process I used:
1. Run gas tank down to less than 1/2 full - closer to 1/3 full.
2. Pour in an entire gallon of lacquer thinner. You can buy these at Lowe’s for $21.
3. Good on a road trip and run the engine without stopping until it is very low on gas. As you get near the end of the tank, run it at high RPMs for extended times to get the Cat very hot and burn out the buildup. I would run mine around 5K RPMs for about 45 seconds, then back off a bit, and back up again, and did this about 20 times. Don’t overheat your engine, but get that baby cleaned out.

After doing this I haven’t got the codes in over 2 years. I hope this is helpful to others. Replacing these Cats is very expensive and very difficult to do, even for those who do their own mechanic work.
Scott,
You make a really great contribution to my meager DIYing.

As someone new to cat troubleshoot (beyond the occasional o2 sensor repl.), one question / knowhow request on the cat "repair" you mention (as I try to discern between your 2008 cat "extension effort" and my 2008 cat ???????-effort...
Your probably wasn't putting out noticeably noxious fumes? (I'm still getting the noxious fumes even after O2 sensor work).

I know my Bank1 cat is not working, but just not sure how far gone it is... LOL Just when I thought I was understanding how downstream o2 sensors DON'T work (feeding back on mixture) turns out that THESE 2008 DOWNSTREAM o2 sensors are really UPSTREAM o2 sensors for the rear cat, and probably DO work to feedback on mixture. My little brain is melting down (and it's not even made of a ceramic honeycomb).

As I was saying all this uncertainty ... and then I have to try to "compute" on WHAT OH WHAT my (recently replaced) little BANK1 downstream bad sensor (itself not its heater) HAD DONE, OH WHAT OH WHAT HAS [IT] DONE.
best, Dan
 
#15 ·
I'm going to try a couple of these suggestions (plus a prior suggestion on this van that I try an infrared gun , if it's even possible to fit it up there / aim it at the two ends of the forward cats, bank1 in my case).

I love it. real-world results are all that I'm looking for... so I don't have to mention you all on some patent application LOL.

Scott: Was yours putting out noticeably noxious fumes? (I'm still getting the noxious fumes even after replacing my bank1 downstream O2 sensor)... Or just both banks' codes?
 
#16 ·
I wanted to share what I’ve experienced as an effective solution for the catalytic converter issues with these aging models. I know there will likely be a bunch of naysayers who cite Scottie as a hack, but I thought this could help some who truly wants to try a low cost solution for these expensive parts. After doing this treatment, my P0420 P0430 codes went away and my engine gained significant power. I’ve done this on both my 2008 Ody and 2008 Pilot with very positive results.
Here is the process I used:
1. Run gas tank down to less than 1/2 full - closer to 1/3 full.
2. Pour in an entire gallon of lacquer thinner. You can buy these at Lowe’s for $21.
3. Good on a road trip and run the engine without stopping until it is very low on gas. As you get near the end of the tank, run it at high RPMs for extended times to get the Cat very hot and burn out the buildup. I would run mine around 5K RPMs for about 45 seconds, then back off a bit, and back up again, and did this about 20 times. Don’t overheat your engine, but get that baby cleaned out.

After doing this I haven’t got the codes in over 2 years. I hope this is helpful to others. Replacing these Cats is very expensive and very difficult to do, even for those who do their own mechanic work.
I tried this process on a 2005 Odyssey Touring with 235,000 miles. Codes disappeared for only 200 miles. I still get 18 to 20 mpg in city/highway driving.

Now I do not care about this code, as I live in a state where there is no annual vehicle inspection.