I don't see anywhere where he says he had P0420 or P0430 cat codes..........

I doubt that lacquer thinner will relieve clogged cats, it only may clean up the cats to help with low efficiency. Once the substrate melts, that's it, it's clogged.

 

What a wonderful thread!
Here is what should have been done to diagnose the cats.
1. Use a Scanner to look at the Ox sensor switching performance both banks by someone who knows what they should be seeing.
This is the first hint that something would be wrong.
2. Do a Back Pressure test with a gauge to verify a plugged condition.
3. Do a temperature check with an Infrared hand meter. The cats work at a greatly elevated temperature when in at least reasonable condition. The Temperature difference would have been seen.
One bank's exhaust header would have been much higher in temperature, as well.
While driving and a sudden change in power occurs, a cat substrate has broken and caused a restriction. The exhaust cannot get out, a new charge has no place to go. The motor (can't breathe). Where have you heard that term, recently?
Why would the attempt to clean this plugged condition thought to be a remedy?
If the cat/s are near dead, the PCM program may put to CEL off because it's no longer any benefit and a drivability issue become apparent hint hint.
In this event, clearing the PCM by power down would have done a diagnostic and set the code anew because they would not pass self diagnostics.
Why would you not expect these things to happen on an engine of this mileage?
I would bet this truck was driven to death without taking care if issues already present, by the sounds of it.
.
If any of you get a new truck past 2015, don't even think about trying to fix it. It's way beyond these years 97-2010 in complexity.
Sorry if anyone gets insulted but......well you know. what I'm saying.

 

I wouldn't. Did you see how many miles it has on it? Over 642,000! It's not going to do that without decent maintenance. I WILL say that 642k on factory cats is a lot more than normally expected. Not surprised at all that they are shot and possibly plugged.

 

"I would bet this truck was driven to death without taking care if issues already present, by the sounds of it."

I am not offended. I just pasted this this quote as a reference. I bought this truck new in 2000. Other than having the transmission rebuilt and having the cats replaced and new tires installed, I have done 100% of the work on it. It just hit 643,000 miles. I rebuilt the engine at about 304,000. One month ago I disassembled and replaced all of the bearings in the differential. I was religious about changing the transmission fluid and filter and as a result it lasted 606,000 miles. The repairs I have made on this truck are too numerous to mention. I literally have a notebook that I keep in the glove compartment that has all of the maintenance recorded in it as well as the milage when each of these repairs were made since it had 272,000 miles on it. I have seen the great things Ford put in this truck and I have seen the, well, not so good like the spark plugs that blew out. ( After the third one blew out I installed TimeSerts in every cylinder) LOL. The old truck runs great except for this issue which I will remedy quick. The right rear cat has to go. I need to do a little research because I am probley going to weld this one in myself. It is a tight fit and seeing what I am doing is going to be a challenge! I need to get past this because lets face it, roughly 640,000 miles is a lot for this little 4.6. In the not so distant future I will need to pull this engine out and rebuild it so it acan make another 300,000 miles!

 

Thank you very much for this info. I do have a question for you on this. On your point #2 you mentioned doing a back pressure test. I have seen this done on YouTube using a vacuum/pressure tester and drilling small holes before and after the cats. They used what appeared to be a brass fitting shaped like a very small funnel slipped on to the vacuum hose attached to the tester. Where can I find a fitting like that? How else can I test it?
Thank you for your help!
Chuck

 

A muffler shop has gauges that they thread into the O2 sensor holes to do this test. If Firestone said that both rear cats needed replacing after you just changed the left rear cat, I'd bet that maybe the FRONT left cat is plugged.

 

I have a question about this. In the "exhaust and intake" section there are a few post about people putting a 94106 in place of their rear cat and moving their O2 sensor behind the new cat. Have any of you guys actually tried this? No CEL's?
Thanks again,
Chuck

 

Yes, you can remove or gut the front cats and replace the rear cats with 94106's, as long as the front O2's are before the cats and the rear O2's are after them. If you do get a CEL, you can use spark plug anti-foulers on the rear cats to fool them.

 

Thank you! It will be a week or so before I can make this happen but I will come back with my results...

 

Thank you guys to the max! Yesterday (Sunday) I replaced that right rear CAT. The front CAT catalyst had broken loose and jammed in the outlet...that is why beating on it produced no rattle. I gutted the front one and welded it all back together....not an easy task. Welding under the truck blindly on the top side of the exhaust pipes was a challenge. Regardless, I got it done. No exhaust leaks and a major increase in power. The transmission shifts as smoothly as it ever did. The 94106 did the trick. I usually clear the codes after doing a repair that has thrown codes, this time I did not. The code cleared itself this morning after several stops.
Thank you again!
Chuck

 

Now to do the same on the left side!

 

That was done about two weeks ago. Still running excellant!