Engine efficiency question

[slravene]

OK ive gotten to a point now where i need to fix a few things... I am only getting about 11 miles per gallon (about 220-230 miles in a full tank). This is with VERY conservative driving. I keep the rpms below 2000 on acceleration, i never floor it, i drive the speed limit, dont idle too long. I dont know what the issue is. I have replaced the air filter several times to no results. I have 3.55 open gears which i know arent the best for 31s but still. I read about guys on here averaging 17 mpg in the city on 31s and etc. The average mpg of most of the threads i have read is about 15mpg city. I would love to get close to that. Are there any suggestions on what i need to do/change to help improve this issue? Thanks.

 

[section525]

Hows the PSI in the tires? How old are the plugs and wires?

 

[slravene]

about 33 psi, and i dont know about the plugs should i change them all?

 

[BuffaloXplorer]

Never just change "some" of the plugs (unless you KNOW only one is bad). If you have never done it, and don't know when it was last done, for $50 (decent plugs & wires) it'd be a good idea.

I've got a '96 and rarely average more than 12 in the city. I recently got 17.5 hwy on a 350 mile trip towing a 1200lb trailer. I cried tears of joy, as i never, ever, ever expected to get 15+ again. I've done all routine & not-so-routine maintenance and nothing seems to help. Driving lightfooted doesn't help, either, so i am always flooring it.

 

[Rhett]

OK ive gotten to a point now where i need to fix a few things... I am only getting about 11 miles per gallon (about 220-230 miles in a full tank).

What makes you think you are getting 11 mpg?
Given your gas tank size and the miles per tank you're getting (220-230) I would have to say you are probably getting 12-13 mpg. The only way to tell is take the miles you've driven and divide by the gallons of gas you've burned.

 

[slravene]

I know how to do math that 220-230 includes some highway miles in it (so i just subtracted a mpg or so to even it out. Last time a actually drove an entire tank in the city i went 213 miles on the tank.

 

[section525]

Yeah, that's not very good. I get better than that in my 5.0L on 33s.

 

[slravene]

its just getting annoying...i shouldnt get this bad mpg and i dont know what to do to fix it. Even when it was stock i was only getting 230-240 per tank on a good day...this sucks

 

[section525]

Well if it's not throwing any codes I'd just start with all the basics. Plugs, wires, maybe make sure the parking brake isn't sticking. Does it smell like it's running rich?

 

[slravene]

doesnt smell like anything but the occasional exhaust smell...I can chance the plugs and wires and stuff, but then what?

 

[CDW6212R]

Clean under the hood(engine degreaser and water hose), carefully check all vacuum lines, connectors, etc. Change the spark plugs and sparkplug wires. The plugs last longer than the wires.

Use fuel injector cleaner every couple of months. Change the fuel filter, install a trans valve body kit(TransGo) and inline filter($10). Vary your driving, drive it easy occasionally, and floor it occasionally.

If the mileage is still poor, start looing at intake bolts(loose), clean the MAF carefully. Without error codes, a last resort might be to change the O2 sensors. Good luck,

 

[Lt.Jim]

Did you adjust your tripmeter to take into account that you are running bigger then stock size tires?

 

[Rhett]

I know how to do math

All right..I was just checking, you never know how people are trying to do the math these days...

First of all, I agree, 213 miles per tank is a little low. But you must keep in mind that you are running the larger tires, and you probably have not changed gears. 31's are not a huge jump, but still that will affect your tripmeter readings, speedometer, and mileage somewhat.

You also cannot expect much more than 230 miles per tank on your setup. The 4.0 OHV engine we have is not noted for it's fuel economy. You said you used to get 230-240 when stock--that is perfectly normal mileage on an OHV.
So if you're getting a little less then that now, it's understandable.

What I would do is what others suggested--normal tune up--change plugs if they haven't been changed in a while. Change wires if they've been in there for 60,000 miles or more.

Clean air filter or replace it.

Do a Sea Foam treatment.

Pull the vacuum hose coming out of the fuel pressure regulator. See if it has any gas in it. It should not.

If you plan to keep the truck a long time, consider switching to synthetic transmission fluid and synthetic oil. While I cannot specifically say this increased mileage on my truck, the total effect of all the mods I've done has raised my average summer city mpg from 13 to 14 mpg.

Of course if you are getting any CEL codes, run them down.

If the O2 sensors have more than 100,000 miles on them, they're probably due for replacement, even if they are not throwing codes.

 

[IZwack]

as an alternative to the sea-foam, you can go to ur local ford dealer and get, i think whats called, an "engine flush".. its basically the same thing as the sea-foam concept.. after the first time my parents took their explorer for this 'engine flush', that explorer drove about 20% more miles per tank up to NY.. the cost is a bit under $100.00 for the flush (call 'em first before u bring ur explorer in and ask for the price)

 

[Skibum1989]

$100!?!?!
A can of seafoam costs about 5 bucks... are you sure it's the same thing?

 

[alexefron]

Clean the MAF, it added a few miles to mine. somehow i managed 19.1 mpg highway last week. But i typically get about 15-16 mpg when doing all city with 3.27 gears, and stock tires.

 

[slravene]

how do i seafoam the engine? Im trying the cheapest methods of fixing this issue first

 

[Skibum1989]

http://www.seafoamsales.com/motorTuneUpTech.htm

...or do a search on this website, there are many many pages and pictures on methods of seafoaming an engine.

 

[BeauJ]

I bought my explorer with 28,000 miles on it. An old woman owned it before me so I know she didn't dog it. Even then, I got maybe 14 MPG in the city. Ever since going to all synthetic, I've stayed at about 13-14 in the city.

 

[IZwack]

$100!?!?!
A can of seafoam costs about 5 bucks... are you sure it's the same thing?

yes.. its pretty much the same thing.. i think the general term is "decarbonizing" or someting to that effect.. most of that 100 dollars at the dealer is the labor.. in other words, they do it for u.. seafoam is just a can... no dude comes with it..

since this is about gas mileage, i took apart the upper intake man. about 2 months ago (SOHC engine, two piece plastic) and cleaned that up really good.. gained about 15-20 miles per tank (was quite impressed).. the plastic parts were coated with this thick, rough, dark brown deposit.. scrubbed all that off so it was smooth black plastic again (it took a lot of time, the deposit is theeeeck)..

oh and during this process, a leaf fell into a valve.. wooOO look mr. leaf says hi to mr. valve on cylinder 6.

.