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3 Catalytic Converters? Tags catalytic converter hfpc Jump to Latest ToonasFirstHonda I was always under the impression that cars have 1 catalytic converter, under the car. I knew they were also related to the emissions of the car. In my other threads I mentioned I was having some problems with my 2010 Accord V6 3.5L Coupe. Weird shift intervals, lagging going uphill, etc. I thought I needed a new torque converter but when I took it to a shop that specializes in Honda/Acura, they told me I needed to replace the 2 cats connected on either end of the engine. That was how I found out my car has 3 cats? I'm asking for someone to explain 1) how do those 2 cats function/malfunction in relation to the one under my car and 2) does replacing the 2 cats(suggested to do so with HFPCs) seem like it will remedy the problems I've been having? Many thanks in advance... 1 - 14 of 14 Posts

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0 I was always under the impression that cars have 1 catalytic converter, under the car. I knew they were also related to the emissions of the car. In my other threads I mentioned I was having some problems with my 2010 Accord V6 3.5L Coupe. Weird shift intervals, lagging going uphill, etc. I thought I needed a new torque converter but when I took it to a shop that specializes in Honda/Acura, they told me I needed to replace the 2 cats connected on either end of the engine. That was how I found out my car has 3 cats? I'm asking for someone to explain 1) how do those 2 cats function/malfunction in relation to the one under my car and 2) does replacing the 2 cats(suggested to do so with HFPCs) seem like it will remedy the problems I've been having? Many thanks in advance...

greg1c

· Registered Joined Aug 10, 2013 · 5,957 Posts Reaction score 1,990 Location Hotlanta If those catalytic converters are bad you will have either a P0420 or P0421 code or both. The 3rd catalytic converter has no sensor to tell if that converter Is bad. The 3rd catalytic converter goes bad all the time. Sent from my Pixel 5 using Tapatalk

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0

greg1c said: If those catalytic converters are bad you will have either a P0420 or P0421 code or both. The 3rd catalytic converter has no sensor to tell if that converter Is bad. The 3rd catalytic converter goes bad all the time. Sent from my Pixel 5 using Tapatalk Click to expand...

The 3rd one being the one under the car? I know one of them doesn't have an O2 sensor.

greg1c

· Registered Joined Aug 10, 2013 · 5,957 Posts Reaction score 1,990 Location Hotlanta Correct the 3rd one is under the car, each bank has a separate catalytic converter. Those are all monitored with sensors. The 3rd one is not monitored. Sent from my Pixel 5 using Tapatalk

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0 I am really just wondering if the HFPCs are gonna solve my problem because while I do want to make a couple of performance upgrades, I don't wanna drop all this money for parts and labor and be stuck with the same issues.

andrewtl96

· Registered 2014 Accord Sport MSM Joined Aug 10, 2018 · 396 Posts Reaction score 305 Location Simi Valley, CA, USA

ToonasFirstHonda said: I was always under the impression that cars have 1 catalytic converter, under the car. I knew they were also related to the emissions of the car. In my other threads I mentioned I was having some problems with my 2010 Accord V6 3.5L Coupe. Weird shift intervals, lagging going uphill, etc. I thought I needed a new torque converter but when I took it to a shop that specializes in Honda/Acura, they told me I needed to replace the 2 cats connected on either end of the engine. That was how I found out my car has 3 cats? I'm asking for someone to explain 1) how do those 2 cats function/malfunction in relation to the one under my car and 2) does replacing the 2 cats(suggested to do so with HFPCs) seem like it will remedy the problems I've been having? Many thanks in advance... Click to expand...

The cats at the manifolds are referred to as pre-cats... which are what the name entails. They are close to the manifolds so they heat up quickly to help burn off emissions, as the rear cat's tend to take longer to heat up. As I understand, the the 3rd cat is more like a standard catalytic converter. If your car runs rich or burns oil, than that can cause the pre-cats (and 3rd cat) to clog up over time. Only real way to know if they are clogged is to remove & inspect them. If they are in fact clogged up, then that's what is causing you to have a performance problem. The oxygen sensors read the amount of oxygen in the exhaust, and they basically tell the ECU the fuel mixture & if the cats are functioning or not. I will say this, after changing from stock cats to hi-flow cats on one of my G35's... they will make the car much much louder. Be prepared for that. BUT, they made the car run much much better!!!

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0 When you say

andrewtl96 said: The cats at the manifolds are referred to as pre-cats... which are what the name entails. They are close to the manifolds so they heat up quickly to help burn off emissions, as the rear cat's tend to take longer to heat up. As I understand, the the 3rd cat is more like a standard catalytic converter. If your car runs rich or burns oil, than that can cause the pre-cats (and 3rd cat) to clog up over time. Only real way to know if they are clogged is to remove & inspect them. If they are in fact clogged up, then that's what is causing you to have a performance problem. The oxygen sensors read the amount of oxygen in the exhaust, and they basically tell the ECU the fuel mixture & if the cats are functioning or not. I will say this, after changing from stock cats to hi-flow cats on one of my G35's... they will make the car much much louder. Be prepared for that. BUT, they made the car run much much better!!! Click to expand...

When you say they made your car run better, was your car having issues or did it just improve what was already functioning well? Also, whats your opinion on if I should get the HFPCs or just get no frill cats?

DIY Fan

· Registered Joined Mar 27, 2020 · 366 Posts Reaction score 362 The advantage of High Flow Pre Cat(alytic) converters is they offer less restriction to the exhaust gasses and therefore a horsepower increase. Usually the no frill (OEM style) cats work the same as factory and are therefore equally restrictive. The increase in sound level with HFPCs is a byproduct of their lower restriction. I have read that some HFPCs burn out (lose their ability to decrease pollution) and will throw a CEL after a few years. So if you want more power, are willing to pay for it, can live with increased exhaust noise, and are willing to risk the need to replace them again after 3 years then go for HFPC. If you do not need increased power, or do not want louder exhaust, or dislike the idea of their possible short life, then stick to OEM style. It is your choice and money. Good luck!

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0

DIY Fan said: The advantage of High Flow Pre Cat(alytic) converters is they offer less restriction to the exhaust gasses and therefore a horsepower increase. Usually the no frill (OEM style) cats work the same as factory and are therefore equally restrictive. The increase in sound level with HFPCs is a byproduct of their lower restriction. I have read that some HFPCs burn out (lose their ability to decrease pollution) and will throw a CEL after a few years. So if you want more power, are willing to pay for it, can live with increased exhaust noise, and are willing to risk the need to replace them again after 3 years then go for HFPC. If you do not need increased power, or do not want louder exhaust, or dislike the idea of their possible short life, then stick to OEM style. It is your choice and money. Good luck! Click to expand...

Whats the lifespan of the OEM cats? Car is a 2010 and I need to replace them now. I'm guessing the VCM is the main cause of this problem. I installed a VCM tuner about a month and a half ago and the issues subsided a bit but here I am needing 2 new cats🤷‍♂️🤷‍♂️

capkirk123

· Registered 07 Accord Sedan EX V6 Auto Joined Sep 19, 2020 · 1,614 Posts Reaction score 1,644

ToonasFirstHonda said: Whats the lifespan of the OEM cats? Car is a 2010 and I need to replace them now. I'm guessing the VCM is the main cause of this problem. I installed a VCM tuner about a month and a half ago and the issues subsided a bit but here I am needing 2 new cats🤷‍♂️🤷‍♂️ Click to expand...

My car is a 2007 and the cats still work fine. VCM probably just clogged your cats with oil.

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0

capkirk123 said: My car is a 2007 and the cats still work fine. VCM probably just clogged your cats with oil. Click to expand...

So can my stock cats just be cleaned out? Or do I have to replace them? Jus wanna be able to take off at a green light and not have to give it gas to reach a red light haha

capkirk123

· Registered 07 Accord Sedan EX V6 Auto Joined Sep 19, 2020 · 1,614 Posts Reaction score 1,644

ToonasFirstHonda said: So can my stock cats just be cleaned out? Or do I have to replace them? Jus wanna be able to take off at a green light and not have to give it gas to reach a red light haha Click to expand...

I don't know that you can clean them. You could try to run the engine hard and burn out whatever is fouling the cats, if you can get them hot enough it should clear them out, but they might be too damaged already. Also, I'd make sure it's the cats causing the issue, otherwise running the engine hard could be bad.

ToonasFirstHonda

· Registered 2010 Honda Accord Automatic V6 Coupe Joined Apr 26, 2021 · 41 Posts Reaction score 0

capkirk123 said: I don't know that you can clean them. You could try to run the engine hard and burn out whatever is fouling the cats, if you can get them hot enough it should clear them out, but they might be too damaged already. Also, I'd make sure it's the cats causing the issue, otherwise running the engine hard could be bad. Click to expand...

I'm pretty sure its the cats. Was having the lagging/shifting problem for a little bit but I brought it to the mechanic the day it kicked a CEL and he mentioned a code when he scanned it, I just forgot what it was. His recommendation was to change out the cats. I don't think I'll be running the car THAT hard at all to be honest. Until the problem is resolved at least.

WiiMaster

· V6 Supremacist 😎 Victus - 2012 Honda Accord (EX-L V6) Joined Dec 24, 2018 · 6,977 Posts Reaction score 7,383 Location Dallas, TX, USA Yeah, VCM will foul up your cats. See the recent video South Main Auto did on an Odyssey for an extreme example: But since you have VCM disabled now, it shouldn't be an issue with any new cat. 1 - 14 of 14 Posts Insert Quotes Post Reply

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About this Discussion 13 Replies 6 Participants Last post: WiiMaster Jul 9, 2021 posts 2.1M members 148K Since 2003 Drive Accord forum, a community where Honda Accord owners can discuss reviews, service, parts, and share mods. Show Less Full Forum Listing Explore Our Forums The 8th Generation The 7th Generation The 9th Generation The 10th Generation Audio, Electronics & Lighting

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