P0420 Code
 

Clearly we all know it's a catalyst issue (bank 1) and it probably will need to be replaced. My question is, several other things could have caused it because a converter (from my very limited knowledge) is not exactly a wear and tear item. Replacing the part can be done of course, but what caused it? Some of my research says faulty O2 sensors, but I would assume it would throw a code as well. I also saw that it could be a misfire (no codes for that) as well as oil contamination (I am burning oil).

What has all of your experiences been? I can change O2 sensors easily.

It's a lot more likely it's the oil burning than it is the O2's themselves. How much oil does it burn?

Let's see...a little over 3k since I last changed it. About 4 quarts gone. Yes I do fill it, but that's about what disappears.

4 quarts in 3k will definitely screw up a cat. Year and engine, please?

2004 f-150 fx4. 192k, 5.4L. I need to do a compression check.

A malfunctioning PCV system can cause oil consumption.

Yeah I have read about that, but there is some confusion on whether it exists at all. Even some disagreements on location of it. How do you test a PCV?

My 05 5.4 is consuming about that much oil...I'm at 155K miles...I get P0430 codes with each tank of gas...maybe its my gas cap? Have been getting the code for about 3 years now...Gas mileage has been about 10.8mpg city, 13 hwy the whole life of the truck...

I highly doubt it's the gas cap - bad gas caps trip evap codes.

Whether the PCV is a valve or fixed orifice, figure out what you have and clean it.

4 quarts in 3k miles is crazy, my '05 only used about 1 quart in 3k, and I have a leaky rear main seal, not burning oil

not going to fix it either, it can leak...

After reading this thread, I'm glad I got rid of the 5.4 I had. And it got lousy mileage too,was averaging 11.3 mpg when I traded it in.

I still get about 13.4 on average.