P0420 is a bad cat or an exhaust leak.

 

this is my writeup for zach at the dealership

Zach
2004 F150 FX4 5.4L 3V

Before the problem…

I bought the truck with 53k on it 2 years ago. Has never had an issue engine-related until a month ago. I had some misfiring and a lot of stuttering after going through a car wash. Found that two coils were bad and replaced them. While replacing the coils, I decided since I had around 90k on the truck, I would get the plugs changed as well. So plugs and coils were changed a month ago. I then noticed my radiator fluid was nasty-looking. So I had it flushed. In the time flushing it, I manually bled the system. I didn’t know that Ford had a special tool to bleed the system. So I let it bleed overnight and kept the defrost on hot while driving for at least 3 days or so. The fluid level stayed the same and the truck ran great. I got a lot of gunk out of that previous fluid and I think the owner before me tried putting the wrong stuff in it or some stop leak because I have never seen them build up like that. It was orange gunk. . (I WANT THIS THING FLUSHED AGAIN TO BE SAFE).

Also, my fan clutch is chirping so I ordered the replacement and plan to install that as soon as you guys are done with it… I don’t think the bad fan clutch could cause any of these symptoms? Again, you guys know more than me on this.

The problem…

A week or so after the coolant flush, I threw a P0420 code…which points me to a low threshold on Bank 1 (02 sensor/cat clogged). This is not good because although I need to fix the code, I need to find out what is causing the issue! I was thinking fuel injector because I have noticed a very very slight fuel smell at the exhaust, but nothing that seems way too rich. What points me to something other than a fuel injector is that I am getting 18.4 mpg on highway and 16.6 mpg in the city. Mixed I am getting 17.8mpg. With a stuck injector or bad injector, I would think I would have hard starts/horrible fuel mileage. The truck runs great!
The only small thing I have noticed is that the truck surges just a tad when warm and coming to a stop. I am thinking this may be the 02 causing it. Maybe the upper 02 which deals with air/fuel ratio. Maybe that is what is causing it to run rich?

My Thoughts…

If it is injectors, replace them under my base care warranty that I purchased. I have the injectors covered until oct 2016 or 105k miles. I also know that Ford put out a letter (recall) stating they covered the damage caused by the injectors as well as the injectors. (So if a bad cat and 02 sensors were caused by the injector, they should be covered).

I have also noticed that ever since I bought the truck, it has idled when in drive and warm around 550rpms….which seems a little low. I don’t know how this is related to an injector issue but who knows.

Also, I have had clogged cats before and when I did, I would put my hand up to the exhaust and would barely feel any air coming out. This does NOT seem the case with this truck…but again, the cat could be just clogged enough to throw the 02s off.

Lastly….

The last 2 dealerships (Inskeep and Capitol City Ford) have been terrible with handling me for small issues. They charged me for things that were not malfunctioning at all and I was charged for an alignment when they couldn’t even align it. They told me my frame was bent…went to Riley Park tire, got an alignment and truck has driven perfect. I understand how dealerships work and I am hoping that since I bought the truck from you guys that you could give me good service and treat me right. Just be honest with me about things.
Thank you for your time.
ONE OF THESE NEEDS TO GO TO ZACH in service so that he knows what my complaints are.