I picked up a used 2004 F150 SC Lariat 4X4 with the 5.4 engine. It has 45k miles on the clock. I took a new 2007 SC with the same motor for a test drive a while back it is seemed to have way more power than mine.
Mine seems to be lacking air movement in the engine. I checked the air cleaner it is good. I have not changed the fuel filter. The truck is completely stock drivetrain and exhaust wise.
It has a 2"lift but factory tires.

How can you tell if the cats are plugged up? I have looked at the exhaust and there is no sign of any excessive heat build up that you would see from a plugged cat(s).

New to this truck forum. I have an 05 Mustang GT and spend a fair bit of time learning about it from the Stang forums. I have worked on vehicles for years, not a rookie here, but this one seems a bit odd.

Please chime in.

 

i think you can have your exhaust pressure tested somehow. usually when they are broken apart inside you can tap them with a rubber mallet and hear it rattle. i think cats are warrenteed until 80k.might get the dealer to take a look at it.

 

I spoke to the dealer today and the exhaust is still under waranty. I have to pay for the diagnosis to see if they are plugged. If they are, then I get the diagnosis and the repair covered. If they are not, they I am out as much as $79, not a big deal. I am going to get the transmission flushed and get them to look at the catalytic converters as well. I will post results later next week.

 

Gotta Pay For The Diagnosis Lol. They Always Get You Somehow. 79$ Isnt Bad Though.

 

Is the 2004 a three valve engine? If not, it has 35 less HP. Also, rear gears can make a big difference in how powerful a vehicle "feels." The 2007 probably had 3.73:1 gears - what does your 2004 have?

A clogged exhaust can usually be detected with a vacuum gauge. Less than $10.00, and you get to keep the gauge.

 

It does have the 3V engine. I am going to change the fuel filter first just to be sure it is not that, plus that is easy to do. I have to take it in for a transmission flush anyway and the $79 is the worst case scenario, they said it will likely be less than that.

 

Before you pay that 79 bucks I would call around to a few exhaust shops. There are a couple exhaust shops in my area that will check cats for free.

 

Good idea, I will try that first.

 

how do you go about testing the exhaust pressure with that vacumn gauge??? that would be good to know.anything that keep us away from the stealership is good.

 

You are indirectly testing the back pressure. The more back pressure, the less air flow through the engine, the lower the vacuum. A severely clogged exhaust system will cause the vacuum gauge to start falling after the vehicle idles for a few moments. A slightly clogged system can often be detected by reving the engine to a couple thousand RPM and holding it there. After the initial dropoff, a healthy engine will regain its idle vacuum and hold it steady - high exhaust back pressure will result in the vacuum slowly dropping off. A vacuum gauge is a very valuable, yet inexpensive tool to have in your toolkit. You can detect worn valve guides, burnt valves - even tell if your buddy is BS'ing you about his "stock" cam.

 

Well I changed the fuel filter and it made no change. However, the crap that came out of the "in" side of the filter was brutal. I looked like muddy water (gas) coming out of the thing. The "out" side of the filter was clean so the filter was obviously doing it's job, but I am sure it needed changing.

The exhaust is getting checked next.

 

so what would be the best pace to hook the gauge up?? any vacumn line on the intake????

 

Any direct connection point - i.e., one that isn't controlled by a solenoid.