Grandma's car P0420

My grandma's car is coding a p0420. The car is a 97 Taurus with the standard engine. I cleared the code the other day with a code reader and now it is back. Can I switch 02 sensors from bank 1 to bank 2 to see if the problem follows an 02 sensor (hopefully)? I assume the sensors are the same for both sides? I have more time than money. If it turns out to be a cat, I think she will just get use to looking at the light. I have also read about trying burn the carbon out of it, so to speak, drive it hard to get the cat hot. Any other ideas? I have a Actron CP9180 scanner so I can get some readings if that helps.
Thanks for any help.

There have been a few other postings for similar codes on Taurii. Unfortunately, no one has reported back as to if they got their car fixed or not.

I'd suggest you use the "Search this forum" feature from the Taurus forum main page and search for P0420. At least one of the posts lists quite a bit of info on items to check.

-Rod

"drive it hard to get the cat hot." First I'd put some fuel injector cleaner in and take on the Inteerstate and run it 75 mph for 15 minutes or so and that should burn out the built up crud. Will it cure the sensor problem? I doubt it. They're like $45. bucks and you can rent the tool at the parts store and change it yourself. Far as I know the sensors are all the same.

"Will it cure the sensor problem? I doubt it."
Is it a sensor problem? I would be happy to install a sensor, it is the 600 to 1000 dollar converter that am worried about. I did swap both upstream and downstream O2 sensors from side to side. Then I went for a drive of about 12 miles driving as fast as legal. Watching the O2 sensor voltage for bank 1 sensor 2 the voltage was "clocking" until I turned around and punched the gas and then the voltage was steady for the whole drive back.

"Is it a sensor problem? I would be happy to install a sensor, it is the 600 to 1000 dollar converter that am worried about." If you ever saw the inside of a cat it is a bunch of small holes and the platinum inside makes them expensive. Cars aren't made to run meidocre slow all the time so periodically they should be taken on the hiway to get them up to crusing speed and hold it there so it can get hot enough to blow out or burn out the crud build up. I don't think driving 55 for 12 miles will do it. You need to get it on the Interstate or someplace you can legally let it honk for a half hour at 75 mph. Not only will it blow out the engine & exhaust but the engine oil needs to get hot to do its cleaning job right.

If you let the cat get pluged up BAD it causes back pressure and the conmbustion chamber retains heat that should have been blown out the exhaust and that can result in burning exhaust valves and/or other expensive problems. If you don't get it fixed soon then I beleive spring for a new cat would be the cheaper, easier way out

I'd say blowing it out would be the first order of business and make sure the tires are good so you can do it safely and obey the speed laws and don't get a speeding ticket.

Off the top of my head, is this the code that, after all is exhausted(no pun), the end result is a bad cat??? Pal of mine had this, I believe, in his case, it turned out to be something fuel-related.. he had asked me about this code, was worried it may be the cat, it wasn't.. I'll try to get further info on this

The code has not come back yet. I will post if it does. The 12 mile drive I agree is not enough, I was watching the O2 sensors more than anything. I will drive it like I stole it sometime this week.

I may not be contributing anything by saying this - but for a period of about 8 months, my car had a lot of short trips - I mean 5 one mile trips a day. The gas mileage went down, obviously, and the car started to not run so well. A 3000 mile trip helped a lot. The car ran a lot better afterward.

Same with the wifes Marqui short trips to work and errands around town with an occasional trip to Charleston, Augusta or Savannah blows it out and if it doesn't get on the road for awhile I take it for a 16 mile blow out to keep it's muscles flexed.

I went on a 475 mile drive today most of the trip at 75 mph. The light has not come back but watching the O2 sensors on the scan tool sensor 2 on bank 1 was never very steady. At 75 mph sensor two would clock and follow sensor one closely. At 65 mph sensor two would clock less but not as steady as bank two sensor two. I'm afraid bad cat.

If the post-converter sensors are changing voltage rapidly and swapping the pre- sensors to the post-position doesn't change anything, you have a bad/failing cat.

Did the MIL light again?

If the post-converter sensors are changing voltage rapidly and swapping the pre- sensors to the post-position doesn't change anything, you have a bad/failing cat.

Did the MIL light again?

Just to be clear I didn't swap sensors from pre- to post cat. I swapped them from blank one to bank two thinking that if I had a bad sensor in bank 1 and moved that sensor to bank 2 I would get a new code of P0430.


MIL has not come back since, but this car is not driven much.


I agree probably a bad cat.

If you do determine that the catalytic converter is bad, make sure you determine why it failed. It's pretty rare for converters to fail for no reason. If you don't remedy the cause, you'll be buying another converter in the future.

-Rod

What would be the typical causes of the cat to fail? My 95 3.8L Windstar gave me an awful fit a few years ago unexpectedly, ruining a fun day for the family. The van made an awful, loud, high pitched rushing sound. At the time I didn't understand what was causing the problem, but the ports on the egr tube that go to the dpfe and the exhaust pipe, were blasting exhaust gas and burning up the dpfe tubing. I thought the tubing was going bad. but realized the exhaust was plugged. I finally convinced myself the cat was plugged. When I cut it open, I did not expect what I saw. The cat has two honey comb like sections that fill the entire inside of the cat that the exhaust passes through. Well, the down stream one came loose, and just kept rattling around, becoming the shape of a football and then the exhaust would shove it into the funnel like exit of the cat, plugging. The cause, manufacture defect would be my guess.

I'm no exhaust expert, but my understanding is the catalytic converter contains a catalyst (platinum and a few other elements) and its purpose is to convert unburned fuel in the exhaust into water. As with many reactions, this produces heat. Normal amounts of unburned fuel don't overwork the catalytic converter, but if your car constantly runs in a rich condition, this will cause the converter to generate A LOT of heat, and high heat is one of the most common causes for catalytic converter damage. I'm not sure if this damage normally occurs in the form of the honeycomb becoming plugged, or if the heat would cause the honeycomb to break loose. I'd suspect the latter though since thermal stress will often lead to physical failure such as materials breaking.

-Rod