2004 4.0 XLS vin k miles per gallon question

[jbwilson3791]

Can anyone else with with this model tell me what kind of fuel economy they are getting? Mine always seems to be between 10-12 mpg city. I know I shouldn't expect great gas mileage with this vehicle but I think it can do a little better than that. This car only has 60,000 miles and is in immaculate condition. Also There are no emissions codes, has new spark plugs, fuel filter, tires, air filter, 1 brand new catalytic converter/ 1 original. I have very fuel efficient driving habits as well and don't use the flex fuel. Anyone have any ideas abut a possible problem or is this about what everyone else gets? Thanks in advance!

 

[Number4]

When my wife drives the '05 4.0, she gets 13 MPG according to the message center, so it's probably less. I get 17 mpg. The difference? She "gasses" from a stop and "gasses" it to the next stop line.

People pass me from a stop light and I let off the gas when I know I'll be stopping.

 

[jbwilson3791]

When my wife drives the '05 4.0, she gets 13 MPG according to the message center, so it's probably less. I get 17 mpg. The difference? She "gasses" from a stop and "gasses" it to the next stop line.

People pass me from a stop light and I let off the gas when I know I'll be stopping.

Maybe I'll work on my acceleration and see if that helps. I really don't floor it but I'm sure there is room for improvement. When it comes to braking I am always thinking way ahead so I don't hurry up just to stop. I suppose I could try some fuel injector cleaner and perhaps a new gas station

 

[Number4]

Out of curiosity, what gas have you been using?

 

[Stick4503]

Same low mileage for me. Best ever was a several hour interstate drive and it managed to get about 15-16. Thank goodness gas is under $2 per gallon otherwise I may as well drive a tank I think it would get better mileage.

 

[jbwilson3791]

Out of curiosity, what gas have you been using?

I usually only goe to a few places. It's either Quick shop, 87 octane or hyvee gas station 87 octane which advertises 10% ethanol (yes i understand ethanol gets less mpg) but I think most places use up to 10% and it shouldn't account for the extra 4-6 extra mpg I should be getting city. It also doesn't do well on long trips either, maybe 15 mpg

 

[Number4]

I've always run Shell or Chevron believing they have/have better additives in their fuel. Can't say for a fact, but one way to offer cheaper gas, is to limit your expense (i.e. Less additives.)

Not sure what Quick Shop or Hyvee is, but in CA, ARCO is the cheap gas and my car ran like crap after using it.

If you were to try Shell or Chevron, you might want to reset your PCM first. Or at least do a couple tanks of fuel treatment. Can't hurt, for two or three months.

 

[Bulletslinger]

When my wife drives the '05 4.0, she gets 13 MPG according to the message center, so it's probably less. I get 17 mpg. The difference? She "gasses" from a stop and "gasses" it to the next stop line.

People pass me from a stop light and I let off the gas when I know I'll be stopping.

lol so you drive better! Go Figure!

 

[bogieb]

I get 15-17 mpg. Actually best mileage is on highway going 70-80 mph and I get about 17.5 (+/-) then. When I am oriving to work (not city driving, but 40-50 mph and 10 stop lights/signs in 30 miles) I get 15-16. Of course 4WD use messes with that, but not as much as I thought - I haven't gotten anything as low as yours. Admittedly, I have only had my truck a couple of months, so have no idea how new/old any of the parts are. Use 87 octane, 10% ethanol Gulf gas (thru Cumberland Farms).

 

[jbwilson3791]

I get 15-17 mpg. Actually best mileage is on highway going 70-80 mph and I get about 17.5 (+/-) then. When I am oriving to work (not city driving, but 40-50 mph and 10 stop lights/signs in 30 miles) I get 15-16. Of course 4WD use messes with that, but not as much as I thought - I haven't gotten anything as low as yours. Admittedly, I have only had my truck a couple of months, so have no idea how new/old any of the parts are. Use 87 octane, 10% ethanol Gulf gas (thru Cumberland Farms).

I'm jealous. Just spent a whole week driving efficiently. Filled up and calculated 11.6 mpg

 

[fr0st m0nkey]

I probably get around 13-16mpg in mine running 265/70/17 which kills me because I have hit 20 mpg after a 5 hour car ride on the freeway in our 2013 wrangler unlimited on 35's with heavy ass 20" wheels (speedo/tire size corrected).

 

[bogieb]

I'm jealous. Just spent a whole week driving efficiently. Filled up and calculated 11.6 mpg

I am used to driving stick so tend to get up to speed quickly even with this automatic (not rocket starts, but jeeze do I hate those people that take 9 blocks to get up to 30 mph). Then let her cruise as much as I can in this hilly terrain. But I do watch for slow downs so I can just ease off the gas, not use brakes too much. On highway I use the cruise control on a regular basis. Oh, and mine has the V6, so If you have the V8 that's a whole 'nother story.

 

[jbwilson3791]

I am used to driving stick so tend to get up to speed quickly even with this automatic (not rocket starts, but jeeze do I hate those people that take 9 blocks to get up to 30 mph). Then let her cruise as much as I can in this hilly terrain. But I do watch for slow downs so I can just ease off the gas, not use brakes too much. On highway I use the cruise control on a regular basis. Oh, and mine has the V6, so If you have the V8 that's a whole 'nother story.

Mine is the v6. And the the only thing worse than people taking 9 blocks to hit 30mph are the people who take 30seconds to make a right turn. And I don't really care about the money I could be saving, I just assume if mine is that much worse than everyone's it probably means something isn't right and I like fixing problems.

 

[Number4]

Hook up a scan gauge so you can see live data. Look at your fuel trims. It's possible you're adding fuel to compensate for a vacuum leak, while not setting any codes.

 

[jbwilson3791]

Hook up a scan gauge so you can see live data. Look at your fuel trims. It's possible you're adding fuel to compensate for a vacuum leak, while not setting any codes.

Thanks i think you are on to something! I've kinda always suspected I've might have a vacuum leak, hasn't happened in a while but last winter it would die on me in extreme cold (would always start back up) any advice on what numbers to look for in the data or how to find a vacuum leak?

 

[Number4]

You can spray carb cleaner around the engine compartment, if there's a leak, it'll suck in and the engine idle will change. Spray in "spots." Though you can have a leak and not detect it this way.

If unmetered air is entering your system, the O2's will pick it up and add fuel to the mixture. Positive numbers on fuel trims means fuels being added, negative fuel trims means fuels being reduced.

Fuel trims should really be zero, but they'll bounce around.
There's long term fuel trims which depict how the system has been running. Then there are short term fuel trims which show what's happening right now.

Plus or minus 10 points is supposed to be within tolerance, but to me, that means there is a problem. There shouldn't be more than a 10 point swing. So if the LTFT is -5 the STFT shouldn't be more than +5.

Ideally, long term will be close to zero and short term will go from -1.5 to + 1.5 or so. Somewhere in that area.

This is an interesting read, it's for the 4.6/5.4 but a lot of the info would apply:
http://troubleshootmyvehicle.com/ford/4.6L-5.4L/troubleshooting-p0171-and-p0174-page-2

 

[jbwilson3791]

You can spray carb cleaner around the engine compartment, if there's a leak, it'll suck in and the engine idle will change. Spray in "spots." Though you can have a leak and not detect it this way.

If unmetered air is entering your system, the O2's will pick it up and add fuel to the mixture. Positive numbers on fuel trims means fuels being added, negative fuel trims means fuels being reduced.

Fuel trims should really be zero, but they'll bounce around.
There's long term fuel trims which depict how the system has been running. Then there are short term fuel trims which show what's happening right now.

Plus or minus 10 points is supposed to be within tolerance, but to me, that means there is a problem. There shouldn't be more than a 10 point swing. So if the LTFT is -5 the STFT shouldn't be more than +5.

Ideally, long term will be close to zero and short term will go from -1.5 to + 1.5 or so. Somewhere in that area.

This is an interesting read, it's for the 4.6/5.4 but a lot of the info would apply:
http://troubleshootmyvehicle.com/ford/4.6L-5.4L/troubleshooting-p0171-and-p0174-page-2

Thanks so much for the detailed response, sounds like you really know your stuff. I hooked up my ELM 327, its an iphone compatible OBDii scanner, Im not sure its perfectly reliable but it seems like its pretty good. Here is everything I got, this first picture is a minute after driving at 45mph in regards to the fuel trims.

and here is the complete list of data after a 5-10 mile trip around town that included a few stops

 

[Number4]

Fuel trims looked fine. They can be high when first starting to drive. But yours were still below 10%.

I only know what I've done or read. Always doubt my ability but hate giving money to someone else.

 

[Josh P]

A few tanks of E85 will help clean the fuel system and the engine. I have done this with my van. The 4.0 in my aerostar gets 14-17 mpg around town.

 

[jbwilson3791]

A few tanks of E85 will help clean the fuel system and the engine. I have done this with my van. The 4.0 in my aerostar gets 14-17 mpg around town.

That's not a bad idea. I'll do that, then try to find best quality gas I can and practice good driving techniques and see if I can get to 14 or 15 mpg