Just had my truck in the dealer for heavy fuel consumption. They did a fuel injector clean, changed the fuel filter and then ran a diagnostics on the engine at my request. They told me that both banks are using 20% more fuel than it should be. He said at 4000 rpm im not making enough power that something is wrong but could not find it. He checked the mass air flow sensor and said it was OK. He then told me i would have to bring it back so he could spend more time checking it over.
The truck has not thrown any codes.
Just though i would put it on the forum and see if anyone could be of help or who may have run into this them self.
2004 F150 5.4. Plugs done 70,000 km ago truck has 173,000 km on it.
I'm trying not to put to much into it as im looking at getting a new truck in the new year. So if i can fix it my self all the better.

Thanks.

 

Plugged cats? You have a custom tune? If so, could be corrupted, have you tried putting it back to stock and putting the stock intake back on?

 

Thanks for your reply. I have been running stock now for a few days and I put the stock intake on over a year ago. The truck seems to have a little more power tonight driving into work after the fuel injectors were cleaned. As for fuel economy it's to soon to tell. I just filled up tonight and reset my scangauge 2 so I'll have to wait and see. The dealer wants me to come back on Tuesday to run more diagnostics and more money.

 

If you're getting a new truck soon, just ride it out . . .

 

That's what im thinking.

 

Hey.

How are they determining the power levels - did they dyno it (unlikely)?

How are they determining fuel consumption? What are they using as a reference, to arrive at that "20%" figure? And during what operating regime - idling, cruise, WOT ( e.g. open loop closed loop?)

What are yer A/F's in open and closed loop?

What is yer current litres/hour reading @ at steady 50km/hr, and at a steady 100 km/hr?

Possible mechanical causes - skewed brake pad(s), brake caliper problems, wheel bearings, dragging parking brake, laggardly fron O2's, incipient VCT issues ...

Simple coastdown tests can help determine if it's chassis/driveline-related ( versus engine management ).

Refer to: http://aspeckt.unitbv.ro/jspui/bitst...4030-Paper.pdf

A derivative of the info contained can be used - coastdown can be used to determine more than just Cd. The math is purty strightforward. You already have the diag tools to facilitate non-rigorous testing ( SCT with Livelink, SGII ). The only problem is you don't have a baseline as yer truck is currently exhibiting a concern ( note that fer yer next truck - baseline it when it's still shiney, lol).

BTW - IMHO, yer dealer is trying to accrue Christmas money .... in other words this sure smells buttcrackish to me ...

MGD

 

How long has it been since the gas mileage dipped? I think winter blend gas has begun to make its way to the pumps too, which could be causing this all by itself.

If it runs fine and it's hard to diagnose what's wrong, if there even is anything, I'd just swallow the extra dollars for gas for a few months and never look back once it's gone.

 

The way I see it, it's the next guys problem.

 

Gas Cap?

I wish I were making this up...

I saw some broken white plastic pieces around my filler neck several weeks ago...same color as the internals of the gas cap...so I decided to replace it. Bought a replacement at O-Reilleys. Since replacing it, my dash mpg's have gone from around 10.8 up to 12.3 mpg...I really wish I was making this up!

The truck would barely do 300 miles / tank previously. Now its up to 330+.
I towed a 6X13 cargo trailer about 100 miles on this tank. I'm at 308 miles and its showing 60 DTE...

Its a $13 experiment...Doesn't hurt to try it...

 

Were the cracks bad enough to cause evaporation? Good catch!

 

No visible cracks...but 2 definite broken pieces that I couldn't see where they came from... looked like a piece of a tab.... 0.30"l X 0.150"w with a pointed end (like the end of a zip tie)...I would post a picture, but have never had good luck doing so...

Truck seems to have just a little more pep...fuel trims seem to be more equal....they kinda follow each other now...previously they were pretty far apart.

I have a bad cat also...for about 3+ years (chronic P0430 codes) so that could also be a culprit. I really wish I was kidding with this...fuel economy has gone from 10.8 to 12.3...My hand calculations are usually in agreement +/- with the dash...

Regards!

 

That kind of thinking is getting pervasive, unfortunately. And I persoanlly find it to be rather offensive, and kinda sad.

Look around on here - no small number of folks come here to ask fer advice on the Used vehicle they bought that had unknown pre-existing conditions that the previous owner just kicked to the curb. A problem like this isn't going to be immediately noticeable to the next owner.

Just old-fashioned ol' Bubba I reckon. For shame ....

BSB out.

 

These were the first things i checked. As for how he found 20% more fuel usage was by connecting it to there diagnostic machine. He could see that both banks were using more fuel then they should.
As for coasting my truck coasts just fine and fuel consumption drops off to 1.73 litres per hundred while driving with no throttle input.
As for base line i used to average 14.7 litres per hundred in the summer and about 16.7 in the winter. Now im getting 17.5 to 18 litres per hundred summer and last winter i was up to 20L per hundred.
As for the fuel cap. Well for $15 bucks it worth a check.

 

You missed most of what I was attempting to convey - but whatever ...

Did yer cap pass the last Driveclean test? A gross cap seal failure will produce a code/CEL.

MGD

 

Well im still fighting poor fuel economy. I just filled up today and had to adjust my scan gauge fuel adjustment again. Its up to 20.1%. WTF!
The truck stumbles and feels like it running out of gas going up a hill with cruse control on.
I have been reading about leaking fuel injectors. But i have had no smell of gas under the hood and don't seem to exhibit any of the symptoms related to leaking fuel injectors.
Anybody else have this problem with higher than normal fuel consumption that could maybe point me in the right direction. Its getting cold here in Canada now so my repair window is getting smaller and i can see the dealer circling like vultures for my money. LOL