Poor fuel economy

[Gruz7]

So I bought the truck (2006 XLT 5.4L) quite a few months ago and with the all terrain tires it has on it (40lbs each) it was getting about 13.4 MPG but the previous owner said it used to get to get 15-17 with those tires and he said because of the misfire it was getting less... So I said ok and got all new plug put in but not the coil pack. This seemed to basically fix the misfire but not the gas mileage, I was getting 12.8 MPG after the plugs were replaced and I then drive for a few months with the dash still reading about 12.8 MPG when I then put on the roof basket and reset the MPG and the new average was 12.2 MPG which I was fine with its a reasonable drop due to the resistance the basket causes. But a week ago I had a flat tire and had it plugged and put back and then reset the fuel economy again, 11.8 MPG. This morning I got in and drove to school and got home just now and it's reading 11.1 MPG. I do not consider myself an aggressive driver and I do try to drive sparingly for fuel sake but this atrocious... Since I bought it I've lost almost 3 MPG and I hear some people on here talking about getting 17 or 16 MPG and that isn't even close to me.
What I'm asking is can I diagnose this before I just go replacing odds and ends everywhere?

Some causes I think it could be or parts I think might need replacing are:
(Keep in mind these are all maybes as I'm not even close to sure where to start on this issue...)

Fuel filter
Fuel pump drivers module
PCV valve
Fuel pump
Coil pack
Catalytic converter
Air filter/CAI

Probably other thing that could be causing it but that's all I can possibly think of.

Any help is greatly appreciated because 11 MPG with stock tires and no lift is not good by any means.
Thanks


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[2004XLT]

Are you still having issues with 4wd? If your front axles are locking up you will lose some mpg. I would start with fuel and air filters, also clean maf sensors and throttle body butterfly valve. I gained back about 2 mpg from those things since they weren't done for the first 114,000.

 

[Gruz7]

Are you still having issues with 4wd? If your front axles are locking up you will lose some mpg. I would start with fuel and air filters, also clean maf sensors and throttle body butterfly valve. I gained back about 2 mpg from those things since they weren't done for the first 114,000.

Yes I am still having issues but not really that it doesn't work just that same clunk when the wheels first begin to spin, in regards to that issues I think it's the CVs and I figure while down there I should do the actuators too

But regards to the fuel economy I figure a K&N CAI might help a little and then cleaning the MAF but I've never cleaned the throttle body before is that something as easy as the MAF sensor?


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[Bedrck47]

Guz. One thing that will have an effect on gas mileage is the cold weather. My 01 will read a certain MPG but when I go and start it up on cold morning it will drop .1 or .2 MPG's by the time I get out of the driveway.

Also you can't go by what the previous owner told you.

I can't say for sure about the 06 but my 01 will take about 50-75 miles of continuous
driving for the trip unit to settle down and give better readings.

 

[Gruz7]

Guz. One thing that will have an effect on gas mileage is the cold weather. My 01 will read a certain MPG but when I go and start it up on cold morning it will drop .1 or .2 MPG's by the time I get out of the driveway.

Also you can't go by what the previous owner told you.

I can't say for sure about the 06 but my 01 will take about 50-75 miles of continuous
driving for the trip unit to settle down and give better readings.

Yeah mine is about the same way to get an accurate reading but idk without really changing anything at all it's tough for me to believe cold weather is culprit in my losing about 3 MPG... I guess the biggest problem isn't what is saying my fuel economy is but what has happened to the mileage remaining until E.. It used to get around 380 miles on a fuel tank but I filled last week and saw only around 310 miles, that was just irritating.

Do you think a clogged a cat could be a serious problem for fuel econ? The cat took some beating from the PO (I agree definitely not a guy I would ever really "trust") who never even knew about the misfire and just drive ok it for some time without changing the plugs or coils.


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[Bedrck47]

When you refuel the computer will calculate the miles to empty based on the fuel in the tank and the Average MPG reading. if you were averaging 14 MPG and then filled up the mileage remaining would be higher.

Yes a clogged Cat would affect mileage

 

[Gruz7]

When you refuel the computer will calculate the miles to empty based on the fuel in the tank and the Average MPG reading. if you were averaging 14 MPG and then filled up the mileage remaining would be higher.

Yes a clogged Cat would affect mileage

Yeah that's what I figured... Annoying figuring out the right cat order and they are damn expensive but I think I'll do the cat and fuel and filter then see what kind of mileage I'm getting... What about the headers? ...Exhaust manifold?


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[Hamfisted]

If you don't know when the fuel filter was changed I'd do that first ( Motorcraft FG986B ). Clean the throttle body intake area and butterfly. Throw a couple of cans of Berryman's Chemtool cleaner (Walmart) in the gas tank to help clean the injectors. Do you have a scantool? Are you getting any other codes? If the scantool has a live data feature look at the oxygen sensors and how they're performing. They tell the computer to richen or lean out the gas mixture. Take a can of Chemtool spray (Walmart) and clean out the PCV valve, they're reusable as long as they're cleaned out. None of the brakes are dragging right? If you have it on a slight street incline it easily rolls in neutral right?


-Mike

 

[Gruz7]

If you don't know when the fuel filter was changed I'd do that first ( Motorcraft FG986B ). Clean the throttle body intake area and butterfly. Throw a couple of cans of Berryman's Chemtool cleaner (Walmart) in the gas tank to help clean the injectors. Do you have a scantool? Are you getting any other codes? If the scantool has a live data feature look at the oxygen sensors and how they're performing. They tell the computer to richen or lean out the gas mixture. Take a can of Chemtool spray (Walmart) and clean out the PCV valve, they're reusable as long as they're cleaned out. None of the brakes are dragging right? If you have it on a slight street incline it easily rolls in neutral right?


-Mike

Easily rolls in neutral

Do not have a scan tool of my own yet

As far as I know there's no codes

Probably will replace the PCV and fuel filter because this truck never really received any necessary care

Also I can just pour that directly into the gas tank as cleaner for the injectors?


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[GAINMOB]

the readout from the dash isn't 100% correct either so u cant solely rely on that for the mpg's...u will have to do the old fashion math...u can do the "gotts mod" or by CAI...recommend high flow exhaust such as flowmaster...Gibson...etc and not just the muffler...cat-back system...u can also look at doing rear cat delete...the #1 thing I recommend to improve ur mpg's is a programmer...I have superchips and run the GAS X tune...I see a great increase in mpg's...HOWEVER...I don't recommend going with superchips cuz its a "canned" tune that is set by them and cant be adjusted to performance upgrades or any other changes u have done...

so most go with ECS and becuz ur a member here u can talk with 5startuning in the vendor section or go to their site and tell them ur a member here for a discount...they give 5 custom tunes designed/programmed to ur truck based on what u want...what u have done to it like exhaust/CAI...and future upgrades and u have custom tunes just for u...so if u tow they'll have a tune for that...high performance...mpg's...etc

I got my superchips programmer then a month later 5startuning came to the site...lol

 

[Gruz7]

the readout from the dash isn't 100% correct either so u cant solely rely on that for the mpg's...u will have to do the old fashion math...u can do the "gotts mod" or by CAI...recommend high flow exhaust such as flowmaster...Gibson...etc and not just the muffler...cat-back system...u can also look at doing rear cat delete...the #1 thing I recommend to improve ur mpg's is a programmer...I have superchips and run the GAS X tune...I see a great increase in mpg's...HOWEVER...I don't recommend going with superchips cuz its a "canned" tune that is set by them and cant be adjusted to performance upgrades or any other changes u have done...

so most go with ECS and becuz ur a member here u can talk with 5startuning in the vendor section or go to their site and tell them ur a member here for a discount...they give 5 custom tunes designed/programmed to ur truck based on what u want...what u have done to it like exhaust/CAI...and future upgrades and u have custom tunes just for u...so if u tow they'll have a tune for that...high performance...mpg's...etc

I got my superchips programmer then a month later 5startuning came to the site...lol

Oh boy lol was hoping to put off getting a cat-back for this truck for a little while longer but I guess if that's needs then I'll have to figure something out..
The programmer I was looking at was a simple hypertech programmer so I get an accurate reading when I up the tire size but I haven't looked into any chips yet for the computer, those really make a difference?

And I just ordered the fuel filter from Napa and will be looking at my options for the catalytic converter, I just don't know which one to buy there's a lot of different cats for this truck.
Also I'll see if I can order the CAI in few weeks if that will help out.


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[Skauber]

The PCV valve on the 3v engine from '05 and up is integral to the drivers side valve cover and is a non-serviceable part. If you want to clean it, you need to remove the valve cover. If you want to replace it, you need to replace the valve cover.

 

[Gruz7]

The PCV valve on the 3v engine from '05 and up is integral to the drivers side valve cover and is a non-serviceable part. If you want to clean it, you need to remove the valve cover. If you want to replace it, you need to replace the valve cover.

Really? ..it's not the same as the F-150?


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[Gruz7]

The PCV valve on the 3v engine from '05 and up is integral to the drivers side valve cover and is a non-serviceable part. If you want to clean it, you need to remove the valve cover. If you want to replace it, you need to replace the valve cover.

I thought hat this was what I could replace?

http://www.autopartswarehouse.com/s...pwcid=gglpla&gclid=CJ7Pt4Kwk8sCFQovHwodh1MDfw

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[Skauber]

No, that wont fit. There is no replacement available, other than if you buy a new valve cover.. Apparently, the PCV system is designed as a maintenance free system without a valve in the traditional sense. Im going to replace my valve cover gaskets in the somewhat near future and im gonna inspect the pcv valve then.

 

[Gruz7]

No, that wont fit. There is no replacement available, other than if you buy a new valve cover.. Apparently, the PCV system is designed as a maintenance free system without a valve in the traditional sense. Im going to replace my valve cover gaskets in the somewhat near future and im gonna inspect the pcv valve then.

Ugh well ain't that annoying, guess my next move is figuring out how to clean the throttle body and butterfly and the PCV system all after cleaning the MAF then replacing the intake, fuel filter, and (hopefully: coil packs and catalytic converter). With all that done I don't see how the fuel Econ wouldn't improve...


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[2004XLT]

Yeah, a basic throttle body cleaning only takes an extra minute when you're already in there cleaning the maf sensors. Fuel filter is important too, when I removed the original and dumped it into a bucket it was basically mud in there.

When I bought mine I got 9.5mpg city now I'm up to 13.5-14mpg city..fuel filter, air filter, maf sensors, throttle body, COPs, spark plugs, tire pressure and fixing brake drag was the difference in my case.

 

[Gruz7]

Yeah, a basic throttle body cleaning only takes an extra minute when you're already in there cleaning the maf sensors. Fuel filter is important too, when I removed the original and dumped it into a bucket it was basically mud in there.



When I bought mine I got 9.5mpg city now I'm up to 13.5-14mpg city..fuel filter, air filter, maf sensors, throttle body, COPs, spark plugs, tire pressure and fixing brake drag was the difference in my case.

I don't have the brake drag you speak of but how did you go about fixing that? You just replaced the rotors/calipers/pads?

And what COP did you go with with? Accell seem to be 50/50 and motorcraft are too expensive, I've heard good things about Delphi but again, expensive so I may go with summitracing's brand or something

And yeah I'm sure once I get the MAF clean and CAI installed then cleaning the throttle body will be a simple YouTube video for how-to.



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[GAINMOB]

Oh boy lol was hoping to put off getting a cat-back for this truck for a little while longer but I guess if that's needs then I'll have to figure something out..
The programmer I was looking at was a simple hypertech programmer so I get an accurate reading when I up the tire size but I haven't looked into any chips yet for the computer, those really make a difference?

And I just ordered the fuel filter from Napa and will be looking at my options for the catalytic converter, I just don't know which one to buy there's a lot of different cats for this truck.
Also I'll see if I can order the CAI in few weeks if that will help out.


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yeah ur gonna need a cat back exhaust...don't do hypertech unless they can give or someone can do custom tunes...I HIGHLY suggest to go with 5startuning...$400 and u can tell him down the road u will add CAI...cat back exhaust and whatever else...if u plan to tow or not... and u get a discount for being a member

 

[Gruz7]

yeah ur gonna need a cat back exhaust...don't do hypertech unless they can give or someone can do custom tunes...I HIGHLY suggest to go with 5startuning...$400 and u can tell him down the road u will add CAI...cat back exhaust and whatever else...if u plan to tow or not... and u get a discount for being a member

Alright I'll check them out... Hear anything about superships or edge?


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