I made a few changes (fixes) to my truck when a FI went bad and now my mileage seems to be suffering. Here's the rundown

06 XLT 5.4l Gas 94K miles.

1. Had plugs changed last summer (Champions).
2. Truck was running a bit rough.
3. Changed VCTs.
4. Helped a bit, but not much change.
5. Had #5 FI go bad. (Ran like crap of course, got codes, replaced FI).
5. Gas mileage improved quite a bit.
6. Still running a bit rough even after 2 tire re-balances. Thought is was a shake at high speed.
7. Changed back to Motorcraft plugs.
8. Changed COP boots and springs.
9. Forgot to let the computer relearn and gas mileage went back down.
10. Did the relearn procedure. Truck idles great but mileage is still pretty crappy.

O2 sensors?
CC bad?
Another FI going out?

 

Good move on #7

Is there a tuner involved in this mix? or still factory?
What is your fuel pressure? Has other regular maintenance been kept up with too? Like new air filter or fuel filter?

 

Codes?

 

Ended up selling the truck and got a 14 XLT with 22K miles.

But in case anyone needs the info, it was an all factory 06 and after the FI issue, it did not throw any more codes so who knows whats up. I'm not usre how the fuel tank sensor actually works, but I speculate that the float level sensor has adjusted itself a bit. I used to be able to go over 100 miles before the gauge read 3/4, then it would move quickly to the 1/4 mark. It started only making it 75+ miles before crossing the 3/4 mark, but the last 2 tanks it would hold steady around the 1/2 mark before moving again. The mileage after a real calculation is only .5 worse. All speculation on my part. I don't have to sweat it any more.

 

congrats on the "new to you truck"

 

Congratulations on the new to you truck!
I was going to suggest a compression check. That bad fuel injector may have washed the oil off that cylinder enough to cause wear and low compression on that cylinder. Just a wild guess.

 

Nope, that wasn't it. I checked all the lines and they are correct. The only thing I can think is that the injectors are on too long or almost constantly. It is running very, very rich. How can I check if the signal is correct? My obd tool is not giving any codes that anything of this magnitude is wrong. I think the injectors are fairly new and look to be in good shape, I think the signal is wrong. There may be some kind of short making them stay on way too long. Sorry but everything I read in the blogs said it would not make any negative change in the millage to take out the egr stuff. There are just way too many vacuum hoses and no good diagrams of how to hook them up and to feed exhaust back into my engine just doesn't seem to make allot of sense from a performance standpoint. Did I mention I put an engine from a wrecked 1997 Expedition, same block, it had about 100,000 miles on it, My fuel pressure was 32 psi but was gone the instant that I turned off the motor. I only took off the stuff related to the egr, and plugged the holes, I get an engine check light but I don't care about that, I don't believe that should give me 5 MPG I only get a code for bad O2 sensor left bank, and air temp sensor no good, Vss Malfunction, and a P1504 which I could not find in the book. White smoke from the exaust , no gas leaks anywhere, I think all that gas is going into the cylinders. The injecter were good in the other engine so I don't think that's it but the wiring harness was seriously damaged for the previous owners engine fire, plus lots of brake fluid spraying the wiring harness which I have fixed and checked over the wiring but I am not sure what my meter should actually read to find the short that is making the injectors run overtime assuming there is one, but obvilosly they are putting way, way too much gas in the engine. Yes it's an F250 but it's the same engine and for some reason this posted here when I was online searching for answers. I have a ton of time working on getting this truck moving and I thought I had it won finally but i just have this one more problem to solve. Signed Desparate Phil

 

Phil, I think you may have replied to the wrong thread?

 

Thanks for your suggestions, I seriously don't think removing the EGR is going to give me 5 mpg , and I super cleaned the K and N filter. Every single blogger that posted about it said they got the same or better millage without it, but I if you have direct experience, not just guessing I can't argue but....... I put on a new fuel pressure regulator because I began to think maybe there was intermittent over pressure in the rail, also replaced some fuel lines but no help and I bought a new fuel rail pressure tester and I've checked it 3 times and everytime it is 30 -32 psi. Still no leaks so the gas has to be going into the cylinders, super rich exhaust smells like gas but I noticed the pressure went down to 0 within 10 second\s of turning off the engine, I know it should be holding that pressure so it occurred to me that an injector or maybe 2 is stuck open. What's the best way to figure out which one? Pull the plugs and see which one is black or super clean? Could they all be stuck open? The aren't very old. Any advice? Am I on the right track? What would you experts do besides putting the EGR back on that I already threw away? I always have a check engine light on, other bloggers that remove all the EGR components reported the same, but the engine runs for them with the same or better gas and performance so who cares? I read hours of blogs and opinions before I took that stuff off. I also took that crap off my fuel injected Nissan along time ago and good riddance. Really no problems, ran great for years, seriously. These guys posting on the blogs I read had fuel injection too, not carbs. Those EGR systems cause more problems than they solve and the replacement parts are expensive. Over complicated in my opinion. No Cal emissions here in Hawaii, that volcano up the road from my house pumps more crap into the atmosphere than all the Ford trucks in the world combined, so I'm not worried about a few extra hydro carbons not burned.So maybe I'm an idiot, but anyway, couldn't it be a stuck injector? Doesn't he fuel pressure going down so fast with the engine off prove it? The EGR and the K and N can't effect with the engine off.

 

Phil - again, I think you are replying to the wrong thread!