[b]From what I have read the P0420 is a common problem in hondas.I am calling out to the gurus (Siena & Co) here, to save me and many others like me.
My Car keeps reporting an OBD code P0420 (Catalytic Converter Inefficiency), and in addition my car seems to lose considerable power especially when driving with AC. Also I have poor fuel mileage in the neighborhood of 15 MPG inter-city drive with AC on

I disconnected the dash board fuse connected to my A/F sensor and my car seems to have more power and of course consumes even more fuel. That gave me the incline that my A/F sensor and/or O2 sensor may be bad. I have made a lot of research and I have been able to narrow down the Potential problems to bad O2 SENSOR and Air / Fuel ratio sensor OR Bad Fuel Pump OR Bad Catalytic converter.

Now, here is where my issue lies: I have got seriously limited budget and hence can not afford to replace all parts especially when there is a chance that only one if faulty. Can you advice me from your experience on similar issues. Also how important is it to replace my Spark plugs, they are not really showing any major signs of under-performance.[/b]

Nothing wrong with your o2 sensors.
https://www.nairaland.com/951734/explaining-catalysts-catalyst-codes

If you are experiencing hesitation or loss of power, your catalyst might be blocked

nissparts: Nothing wrong with your o2 sensors.
https://www.nairaland.com/951734/explaining-catalysts-catalyst-codes

If you are experiencing hesitation or loss of power, your catalyst might be blocked

Thanks.I was actually making plans to change the Catalytic converter, so I took it to the mechanic to remove it. He placed his hand behind my car's exhaust to feel the pressure coming out from the exhaust and concluded the CAT was ok; but I insisted that He should bring it out first; He brought it out and everything inside looked intact, I could even slightly see through the cat (like a pinhole camera see-through). Then I felt I should disconnect the fuse to the A/F sensor and there was a remarkable improvement but after driving it like that for like a month I returned the fuse because the fuel consumption was already hitting my pocket hard; but shortly after I returned the fuse, I could feel the loss of power again, then I concluded the A/F sensor was making the car run lean. Then I removed the fuse again for like a month and the half again, and I was soon reminded of my high gas mileage when I fixed my A/C, then I returned the fuse, and the P0420 code didn't show up for about a month and the loss of power wasn't really felt. But now it has showed up and I now feel loss of power when my A/C is on; on a hot afternoon.

Sorry for the long gist, but I wanted to put the problem in the correct perspective. If more guys insist on the CAT, then I would take a leap of faith.

You cannot have an 0420 code for a faulty a/f sensor.
Your cat is either bad or there's an exhaust leak by the cat. Is your car 6cyl?

nissparts: You cannot have an 0420 code for a faulty a/f sensor.
Your cat is either bad or there's an exhaust leak by the cat. Is your car 6cyl?

No 4 cylinders. Ok I will give it a shot then; but is your opinion about hollowing the CAT out still the same. I.E Do you still maintain it is ok to hollow the CAT out using a defouler with it. I think I'd rather try that out before purchasing a new one. If you have a quote for a new CAT for Honda Accord 2003 LX 4 Cylinder, preferably a MAGNA brand. Kindly send it to me.

Yes, hollowing out is a viable option. Just make sure no exhaust leaks are present after the job is done so other codes dont come up.
A new magnaflow CAT will run you 60k.

Meanwhile, also have your fuel pump checked

nissparts: Yes, hollowing out is a viable option. Just make sure no exhaust leaks are present after the job is done so other codes dont come up.
A new magnaflow CAT will run you 60k.

60k?! Men, hollow all the way o. The crux of the matter is where and how are you going to check if your fuel pump is ok. The best I guess the Mechanic will do is pull out the hose and check out how well it gushes it out. Do you think that method is accurate.

The check engine light came up on m car too, a lexus ES300. Scanned it and this same code came on, but on bank 2. Not sure where bank 2 is. Somebody advised me to change the catalyst converter.

Bank 2 is in the front of the engine.
If you have another code coming up with the catalyst code, solve that one first before any thought of catalyst replacement.

diehard: The check engine light came up on m car too, a lexus ES300. Scanned it and this same code came on, but on bank 2. Not sure where bank 2 is. Somebody advised me to change the catalyst converter.

I read somewhere that the back O2 sensor are the ones that actually send signals used to determine the efficiency and status of the Catalytic converter, so if the O2 sensors are malfunctioning, they can actually send out the wrong signals. SOME MECHANICS ADVise you check out your O2 sensors first before changing the CAT.

So I found a place where they use a spectrometer to analyze the O2 sensors and determine if they are functioning well or not; I also plan to get them to check My fuel pump and CAT too. The place looks tech.; it is in KADUNA (CarCraft). I will keep you guys posted. Hoping to do it soon.

If you have a catalyst code and you replace an o2 sensor, 99% of the time you would have wasted your money

What do you advise i do? i live in port harcourt

nissparts: Bank 2 is in the front of the engine.
If you have another code coming up with the catalyst code, solve that one first before any thought of catalyst replacement.

If it is the only code you have then you either replace or do the modification posted earlier.

This question is for all to answer before doing anything then we can all improve our collective knowledge.

If your code says cat is inefficient, what sensor is there that determine it ?

Consider inefficiency is a reduced input to output ratio and the sender sensor that reads that is .....

So here are 3 video sto watch, I posted the cleaning one in an earlier thread not sure the solvent works but it easier than hollowing out the cat, then hope your car is still efficient, if you are wrong it will cost more running with hollow cat.


https://www.youtube.com/watch?v=9VZ5K8n5jj0


https://www.youtube.com/watch?v=5icTmYItwiE


https://www.youtube.com/watch?v=ZO8yUfWAUl8

nissparts:
If it is the only code you have then you either replace or do the modification posted earlier.

@Nissparts, could a hollowed out catalytic converter be responsible for my recent high consumption and loss of power going uphill?

Nope.
What vehicle and what codes do you have?

sultaan: This question is for all to answer before doing anything then we can all improve our collective knowledge.

If your code says cat is inefficient, what sensor is there that determine it ?

Consider inefficiency is a reduced input to output ratio and the sender sensor that reads that is .....

To the best of my knowledge it is the back O2 sensor that signals that error code. From all i have read it is either ur O2 sensors are bad or the CAT is bad, on many American online fora, u re advised to change O2 sensors first because they are cheaper and easier to fix.

JaaizTech:
To the best of my knowledge it is the back O2 sensor that signals that error code. From all i have read it is either ur O2 sensors are bad or the CAT is bad, on many American online fora, u re advised to change O2 sensors first because they are cheaper and easier to fix.

The downstream O2 tells you if the cat is bad, you the scan tool to eliminate O2,in your case you should try cleaning the cat first since it is the cheapeat fix right now. Look at the vidoes

Finally, i did what I should have done a long time ago, but kept procastinating. I CHANGED my Air filter, and now I can feel my car has got more power, perhaps it wasn't my catalytic.converter causing the loss of power afterall.
I resetted my ECM, and at the moment my car has not thrown any code. I will observe it over the next 2 weeks before my final verdict.

sultaan:

The downstream O2 tells you if the cat is bad, you the scan tool to eliminate O2,in your case you should try cleaning the cat first since it is the cheapeat fix right now. Look at the vidoes

Finally, i did what I should have done a long time ago, but kept procastinating. I CHANGED my Air filter, and now I can feel my car has got more power, perhaps it wasn't my catalytic.converter causing the loss of power afterall. I resetted my ECM, and at the moment my car has not thrown any code. I will observe it over the next 2 weeks before my final verdict.

If you had the 0420 beforehand it will be back within the next 1 month or less.
Your air filter may have been responsible for hesitation but it would have to be completely clogged for it to do that.
Good luck

nissparts: If you had the 0420 beforehand it will be back within the next 1 month or less.
Your air filter may have been responsible for hesitation but it would have to be completely clogged for it to do that.
Good luck

I won't be surprised if the code returns, the last time i resetted my ECM it took it over 3 weeks to resurface. But my major worries were not to reduce pollution (which is the primary essence of a CAT), but to get power back into my car. I still plan to replace my CAT, to an Highflow Magna CAT, when I can afford it; I am sure I would get additional power back to my vehicle. In the mean time I am going to experiment with changing my Spark Plugs to brand new OEM ones. I plan to order them, because I guess there is no where you can get original OEM plugs in Naija.

Latest Update: My P0420 code is yet to re-appear but since I changed my Air Filters, my car now gives a humming sound which is quite audible when the car is idling. I made research and I found out this is pretty common with fake after-market filters. Well, if you ever happen to have the same problem, do not panic. Only fake Air-Filters are available in Nigeria.

Incorrect. I sell brand new original air filters

update: P0420 code is back. Hmmm sad, but car still drives better than before.

@nissan do you happen to have bando serpentine belts for accord 2003 2.4 litres engine.

Did you have the cat cleaned in soap as advised?

You need to be sure its not clogged and the core materials can do their job, if you do anything else like remove the material then you no longer have a cat and your o2 will still read funny.

sultaan: Did you have the cat cleaned in soap as advised?

You need to be sure its not clogged and the core materials can do their job, if you do anything else like remove the material then you no longer have a cat and your o2 will still read funny.

My P0420 code have disappeared for over 2 weeks now; this happened after I refilled my tank with Petrol and added a Mobil Injector Cleaner (Mobil power), when I noticed it the first time, I refilled my tank again when it was half-full adding another bottle of the injector cleaner (Mobil power). The code is yet to re-appear since then.

I remember in one of the videos, that the mechanic advised you empty about a gallon of "thinner" into your tank first before deciding to remove it for a wash. Perhaps the Mobil power just did the thinner's job. I will keep you guys posted if it shows up again.

Well, I think I have made some progress on the P0420 code, now I want to figure out how to deal with my poor mpg issue. The car currently does about 16 - 17 miles per gallon on city driving . The car has over 200k miles on it, still drives strong except for a noticeable loss of power when on a/c. IT has no check engine light on at the moment. Accord 2003. Any help is welcomed.

What most Lagosians do not realize is that 17mpg for lagos city driving on our quality of fuel and engine oils is more than adequate for a 4 banger and you will not get better than that until you take a long trip on a highway.

If you buy a brand new Hyundai today for example, you will enjoy between 18-19mpg city driving depending on your route.
At 1000km you will have to take the vehicle in for the first service. Immediately after that service, your mpg will drop to 14-15mpg on the same route. Why? Quality of engine oil used.