People like to change O2 sensors because A) they are cheaper than a cat and B) They are attached to the cat so they must be the issue - FALSE.
Having worked at Ford for many years, I have yet to see a P0420 or P0430 being
caused by an O2 sensor. The sensor itself will generally throw one of two codes, either heater wire failure (doesn't heat up fast enough when truck goes into closed loop) or sensor out of range (very lean, very rich or switching to extremes). There's also the open or shorted circuit issue but that's not even close to what we are discussing. The 0420 and 0430 were designed so that if your O2 sensors ARE WORKING CORRECTLY, they are able to monitor the switches between front and rear to determine how well the cat is working. If they have the same switching action front and rear, it indicates that the cat is not converting gases properly and should be replaced. If it is switching quickly,
it is definitely working. If it is not switching or out of range, it throws an O2 sensor code instead.
Has switching an O2 sensor worked? Yes, rarely. Sometimes a lazy front or fried rear sensor will add to the existing catalytic problems enough to throw the 0430 code before they throw their own code (RARELY!!!! It's not ODB1, codes are a fair bit more specific nowadays and O2 sensors are quick to throw their own codes), replacing them can keep the code off for a while or get through a smog test but it hasn't fixed the issue.
Some say you can and some say you can't CLEAN a cat, on Explorers it's actually quite easy to clean them due to the bolt on style. I've done it with great success before, it has also been scientifically proven too and a full report is available
(direct link to PDF) . Go to a nutrition store, a U-Brew wine and beer store or (in my case) a candle making store. They sell citric acid in bulk (The candle place sells it because people buy supplies to make bath bombs with), you need 1-2lbs, it'll cost about $5 tops (U-Brew sells little packets for $4 each but I get 2.2 kg in bulk for $5.77 from Wix and Wax here).
Pour boiling water in the bathtub or get a giant camp cook-pot on the BBQ to simmer (I have tried the bath but not the BBQ, yet others said it worked well). Add 1lb of citric acid and agitate it with the cat submerged. Slosh it around inside the cat, pour it through etc. Let it sit overnight, add more boiling water, agitate, flush etc. You'll clean any carbon out without harming the precious metals. You will either get black sludge out of it, or it may turn light green from tiny droplets of antifreeze that stick to the converter over time.
To be scientific, the molecules in the converter's precious metals will actually spread apart and clump together over time. Citric Acid is proven to break up and rearrange these molecules to recover the metal's initial composition. (Cool, stuff huh?) Another Acid for cleaning, will actually do more for some of the precious metals while Citric Acid is better for others, is Oxalic Acid, it's found in paint stripping and wood cleaning compound such as Behr's Wood Cleaner. It is also proven safe but I prefer the straight citric powder than someone else's product that contains Oxalic acid, and who nows what else.
As for people using Var-sol in the gas tank or a bath? Maybe if it was a much older vehicle, that's just a bit too caustic for my sensors.
NOTE: If your CAT is actually dead, metals absolutely done for, or it rattles (busted to
pieces inside) cleaning does not work, buy a new cat. Cleaning just helps a carbon clogged cat perform better (like new in a few cases).
If you are here because of your Google search for bathing your kitty cat ,
DO NOT USE CITRIC OR OXALIC ACID!!! Try shaving it and using the washing machine and
(insert generic laundry detergent here), hang dry on the line for a few hours on a sunny day and kitty will be full of life again!
So all that said, and thanks for reading ladies and gents, if you have a P0430 or P0420 on a Ford Explorer (or any other car for that matter) chances are your Cat is not working properly and will need replacing.
They are few workarounds, which are temp fixes at the very best, and you will eventually replace it. Unfortunately, new/aftermarket cats, don't have the same amount of precious metals inside and will be history in less than 5 years. But at $250 a piece for your Ex, what the hell, it's a super quick bolt on anyway.
DISCLAIMER:
I don't carry Explorerforum liability insurance or any other insurance for that matter, besides the stuff the G-men force me to buy in case I run into something/someone with my truck.
If you try any of the above methods and your truck dies or you get drunk and run someone down or you snort the Citric Acid and get a nosebleed or you get busted with the bag of acid in your trunk and they think you're pushing coke or any and all other boo-boos, brain farts and flubs, it's not my fault, okay?
Fix your truck at your own risk!
Good luck and may fixing your vehicle be as pleasant as being kissed by a thousand fluffy kittens.
(LOL, this post is peppered with 'cat' and 'kitty' so many times, it's bound to be Googled by cat lovers looking for grooming assistance.
)