I just recently bought a 2001 F150 4.6 truck. When I got it, gas mileage seemed ok, I didnt take note of how well/bad it was when I got it, but it seemed like a normal amount of gas being used. Since I bought it, I had to replace the COPs and spark plugs and the fuel filter and pump. After doing all of this I noticed a significant drop in how much gas was being used. This time I took note of it and it came out to 11.3 miles to the gallon. At the same time I been dealing with a P0401 code, which I been putting off. I replaced the DPFE Sensor today, and it seems like I am going through gas much much faster now.

What do I need to do or check to find the culprit of gas gulper?

 

How many miles on your truck? Is the air filter clean. Clean the MAF. Put a bottle of Gumout for high mileage engines in a half tank of fuel and run it through.

 

She has got plenty of miles on her, just hit 250K a few days ago. Air filter is new, I put in seafoam in the gas to clean it all out. What is MAF?

 

Mass airflow sensor.

https://www.f150online.com/forums/ar...3-f-150-s.html

Clear the codes and see if any come back. NEVER use Seafoam, it's too hard on cats. Use either Techron or Gumout with Regane.

 

Thank you for that link and the tip about not using seafoam. Had no idea it was to hard on the cat. As far as codes, cleared it out after taking care of the P0401 code I was getting. Since replacing the DPFE sensor and clearing the code out I have not had any codes come up.

 

You have no reference to judge by, whatever.
Just what it looks to be.
You need to run several tanks of gas over the same route to see the average used per the mileage.
The DPFE sensor has no affect on fuel mileage. It is a 'reporting sensor' for EGR testing only.
If here is an EGR fault, the mileage will suffer but for a different reason.
When a fault is present the EGR function is inhibited from operation.
The truck likely needs both front Ox sensor replaced due to age and contamination.
The ports behind the EGR likely need opening up from carbon build up.
Only way to see if there is anything out of limits or lazy is looking at the live data with a Scanner and interpreting what you see.
Putting anything in the gas changes the fuel make up and how the sensors react.
Any additive with alcohol type ingredients adds Oxygen in the exhaust and causes the sensors to add fuel. That in itself will make mileage worse.
Your going about this all wrong and fooling yourself from lack of knowledge about how things work..
Good luck.

 

All I stated is that my gas mileage got way worse after changing the DPFE sensor. Literally in the same day.

But at any rate, I have a scanner that will give me live information, but I do not use it due to I do not know how to interpret it. If I take pictures of the live read out, can someone here interpret it for me?

 

DPFE= differential pressure sensor.
It is used to measure a pressure difference across a .040 hole in a disc in the metal pipe it is attached to with rubber hoses.
The sensor reports the result to the computer as a pass or fail signal.
This is the flow test that failed causing the 401 code.
So the DPFE likely is not faulty to begin with if it reported the test fault.
The DPFE did not affect you fuel mileage where it is located and what it is used for.
Your associations are faulty.
How did you measure the fuel mileage change then put the old part back on and test again?
I'm trying to bring you to the point that you cannot make conclusions like that and be correct.
I'm sorry to challenge you like this but your not getting anywhere doing it the way you do..
This is why you came here because your not getting anywhere..
Good luck.

 

I didnt change the sensor to battle the gas mileage, I changed it due to the code. I know what the sensor does. You are beating the wrong bush, period. All I stated was that after changing it out my gas mileage dropped significantly. To put it in perspective for you, I filled my tank the night before, just as I did the week prior. Using the amount of gallons I put in my tank being divided by the trip odometer, read out near the same, a little over 11 gallons to the mile. I take the same route every day, nothing extra. Now as stated, this was last night I filled up. After switching out the sensor and going the same route I always go, I am already at half a tank of gas. And yes I am figuring in the trip from my house to Auto Zone and back. That is only 2 blocks away.
So as you see, it was a significant drop, with the only change being the sensor. One week to fill tank to near 2 days to fill up again. So you can see my concern. And no it has nothing to do with me adding seafoam, since that was added when I first got the truck over 3 months ago.

Now again, I am not saying the sensor itself is the culprit, (therefore not trying to associate) I brought that information in because it is relevant to chasing the problem that I started to chase today. Since the significant drop came after changing it. There are plenty of things around the sensor I may have accidentally done something to that I did not notice.

So if your not going to help, get off my case, I seen plenty of times here on the forum that you provide plenty of help, but at the same time giving a sense of attitude. And that is not what I am here for.

 

Tell you what, since we are banging heads about all this and you feel circumstantial evidence rules your conclusions, then I will not try to be of help any further because I'm not getting through explaining about how the technical side of the systems work.
.I'm guessing it doesn't matter to you.
Good luck.

 

I swear this guy does not know how to read, like how many times do I need to state that I am not associating the sensor as the reason for my bad gas mileage. You would think it was evident of that with my very first question, On what do I need to do or check to start finding the reason for my bad gas mileage.

Even further more after his first post, I asked if I take snap shots of the live feed can someone interpret it for me.

 

So lets try this again.

If I take a snap shot of my live feed from the scanner, can some one here interpret it for me here on the forums?

 

You would probably need to take a video as you drive and describe what you're doing. Climbing hill, braking, coasting, idling etc. In short, you want to see your LTFTs (Long Term Fuel Trim) pretty much equal bank to bank and as close to 0 as possible. If you see your LTFTs on both banks +30, there is a good chance you have a vacuum leak or your injectors are clogged/restricted/bad spray pattern.

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As Blugrass stated, your o2 sensors are probably crap. If you have 250k on them - that should be your very first step as they are what feed that LTFT and STFT data to the PCM. I don't know about my Fords, but my Dodge is very very picky about the brand of o2 I use. Bosch sensors tripped the CEL and I had to go with OEM (NTK). Maybe someone else will chime in or you can search.

Speaking of search, there are lots of articles about reading live data. Do some googlin dude...

 

I am not sure what you mean by +30, banks, and LTFT, I assume this is info I would find on the live scanner. But you assume correct, I have 2 other trucks as well, and both dodge, Ford is the same way, if its aftermarket stuff, Ford will sooner or later eat it up for breakfast so to speak, and sometime possible have to change something else due to using aftermarket stuff. Ford loves Motorcraft. My O2 sensors are the next thing I replace. I would of thought if those sensors were bad it would throw some kind of code.

But thank you.

 

LTFT = long term fuel trim. Should be relatively even from one bank to the other and close to zero. +30 is a lot of excess fuel being dumped to compensate for unmetered air (air entering the intake after the MAF sensor). Can also be caused by worn out O2 sensors, which may not throw codes.
STFT = short term fuel trim.
banks: Bank 1 = passenger side, bank 2 = driver's side.