Hi Guys, so first off I am new to the forum https://www.f150online.com/forums/im...ilies/Noob.gif and I have read numerous threads about those two CEL codes that have come up in my vehicle (2005 5.4l 4x4), but because I have mixed/varied symptoms, I have had trouble narrowing it down, and was hoping some of you might be able to help me narrow it down.

Here's the skinny... The truck has 203k on it, and I have had it for about a month.

A couple of weeks ago trouble code p0174 popped up, and when I took it to oreilly, there was a kid there with the same truck as me that was almost 100% sure it was the driver side downstream o2 sensor... So I replaced that, reset the codes, and three days later the CEL came back on again.

The next morning, before I can have the codes pulled, the light was off. Stayed off for a week, then came on again 2 days ago, and when I checked the code it was p0430. CEL wasn't there this morning when I turned on and started the car, drove it for about 10 minutes to and from the store.

Now here's some other info.

I have had a gas smell in the cab when I have the ac on, and the vents open (fresh air vs. recirculating), but ONLY at idle. This has been there since I first bought the car a month ago. Disappears at freeway speeds. (Most of the threads attribute this to spark plugs not being properly torqued, and needing to be retorqued.)

ALSO, yesterday what I noticed was that my gas mileage seemed to have suddenly taken a hit... haven't calculated it yet as I haven't filled up since I notice the gas gauge moving a higher than normal rate, but I use to average about 15-16. Based on rough calculations it seems like it is getting 10 now, maybe even less.


I realize that p0430 is normally a bad cat (from what I have been lurking), but since I had an o2 sensor (allegedly) go bad, and a week later a (possibly) bad cat, rather than start throwing $100's and eventually $1000's, at parts that aren't the root of the cause, I decided I would check to see if any of you had any strong hunches.

Thanks for the help!

 

p0174 is not a catalytic fault nor an 02 sensor.
My guess is with your other symptoms is you are having a fuel injector issue. Which the 05's had plenty of. The p0430 makes sense being you are probably washing the cats down with raw fuel. You are well beyond the recall perimeters so any damage caused by faulty injectors would be on you.... sucks.
The typical problem they had were leaking.. which would cause a hydrolock, bent rods etc.. You may be experiencing some symptoms leading up to that. Someone else more familiar with the 3v 5.4 of this year can chime in but that is my guess.