I'm getting 5.5 mpg while towing my 3 car trailer. Normaly, the worst I've ever seen is about 7 or 8. But I usually average around 10 or 11.

Performance is down. No smoke. I've changed all filter's. Had it in the shop several month's ago to test the injector's. They scanned it, not injector kill. Said they did an engine cylinder balance test, and all was fine. But that could be differant now. How should the injectors be tested. No fuel in the oil. I always run some type of injector cleaner too.

The only thing out of the ordinary is the lack of soot. I've alway's seen a puff of smoke in the side mirror at night when a car is behind me. I've alway's read that was normal. Well I'm not seeing that now, and the tail pipe is alot cleaner than normal. Infact, I posted a pic of a crack in my turbo housing. There was soot around the crack,, but it's clean now.

The other thing I find that might be suspicious is low fuel pressure,,,,maybe. I think it just may be my gauge. I'll change that tomorrow to verify. But if it is low pressure, would that cause bad mileage. Could it be a clogged pick up in the tank. Read this link.

https://www.dieseltruckresource.com/...d.php?t=198834

I guess what I'm asking,,,,what all could cause this kind of bad milage. I'm going broke. Just paid $4.09. I'll be out of buisness real quick if this keep's up. I'm getin cut with a double edge sword. Bad milage and fuel price's.

 

If there is no codes and everything else checks out. Then i would check the Fuel Pressure first.

 

Driving habits.

 

I can't imagine your truck using that much fuel and not smoking HEAVY!!!

 

Wow.. are you sure you injectors arent sooted up or worn out?
Id also verify you have decent boost pressure and theres not a leak somewhere.

 

Have a look underneath for a fuel leak with the engine running. If it's not burning it it's leaking it.

 

Bad MAP sensor?

 

If your fuel pressure is down, perhaps there is a leak in a fuel line somewhere? Hopefully that's the case as it may be easy to pinpoint.

 

my thoughts would point to that.

but still it would be smoking like crazy if that was the case

if it was a boost leak and it was dumping fuel it should be smoking like mad.

check for any leaks and i would look into your fuel pressure asap.

 

In my best truck driver voice.

"Well you all ain't gonna believe this".

What ever the problem was,,,,fixed itself. Over the last year I've been getting worse and worse milage.Then yesterday morning I filled up and headed out. Reset the over head. (I know not accurate, but a reading of 10 is better than a reading of 5) It got up to reading 10. This can't be right,,,it's been saying 6. Then low and behold, I went 300 mile's one one tank of fuel. Not only was this an improvement,,I don't think I've ever got that good of milage. At least that I can remember. Filled up again, and got the same great result's. I think I could get 350 mile's out of it. When it was doing bad I would get at 175 and start looking for fuel in a hurry.

I swear I haven't done anything differant. All I can think of is some crud, or clog, or something broke loose. Or a shorted wire freed itself.

I also wonder if you guy's might be onto something with the map sensor. I've never really seen black smoke coming out of my truck. Then a couple of day's before I left, with out the trailer hooked up, I romped on it and seen a cloud of black smoke. It did it just one more time and that was it. Could that be a sign of the map sensor going bad.

BTW. The fuel pressure ordeal was the junk isolator.

 

One inexpensive mod you may want to try out, may give you the best milage boost in this day/age; a locking fuel cap.
Good luck on your search for the truth, and I'm back to my evening beverage ;

 

I don't know much about '04s or where the overhead gets the fuel flow reading to determine consumption, but if you were returning a little bit more fuel to the tank than normal while still delivering the same to the engine, wouldn't that show a false decline in mileage?

 

I just use the overhead for a rough gestimate of mpg. All I know I was needing to find fuel at 175 mile's per tank. Now it's 300. I have no idea what's going on.

 

winter fuel vs summer fuel...

 

My thoughts exactly!