Is there a hole in my gas tank or what!!!!

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captain chaos

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Hi all. New guy here.
Bear with me, I have a tendency to get a bit "wordy"
I just recently bought a 2000 Expedition XLT 4x4 to replace my wifes Jeep Cherokee. The Jeep served us well for many years but we purchased a camper and the little Cherokee struggled a bit pulling it around. We kinda wanted something with 3rd row seating as well since our family is growing and we like taking little day trips with family and friends. We decided to sell the Cherokee and get an Expedition. We searched TONS of options but the Expy just kept coming out on top. We found a well kept one, with the options we were looking for (4.6L, 4wd, non EB; the leather doesn't seem to hold up well), for a good price so we bought it.

Anyway, thus far I LOVE driving the Expedition except for one major problem; the gas mileage. We are both VERY conservative drivers but the Expedition just seems to suck down fuel like mad! I've searched around and it seems like our MPG's are a bit low considering our "grandma and grandpa" driving style (rarely over 2000rpm, in 4th w/ the torque converter locked by 40-45mph, long coasting whenever possible, seldom over 60mph). The first week under "nromal" driving (60% in town/ 40% rural) we got 12.5mpg from it ( just for reference, our straight 6 Cherokee would get 17 under the same conditions: I told you we drive easy :biggrin:). I recently took a little trip with my Dad and brothers to a car show (220mi round trip) and it averaged 15.5 and that was about 90% flat open highway at no more than 63mph (55-60mph speed limits).
My brother's friend would drive his Expy all over the state and average 19mpg from it; what gives?

Here's a few thought I had:
1) mine had a HUGE grill guard on it when I bought it (and for all of the recent driving up until a few days ago). It was the "Texas style" that covered the entire front of the vehicle type. I have since removed it. I'm sure that was costing me 1/2-1mpg on the hwy.

2) I have the infamous "Ford exhaust leak" but it seems to be intermittant. Sometimes it's very noticable (tick.tick.tick.tick.tick) sometimes you can't even hear it. Is it possible that the exhaust leak is causing air to get sucked in and that is making the O2 sensor read a lean condition and thus adding fuel to the engine when it's not needed?

3) The pervious owner was FANATICAL about maintence. I talked with him a LONG time before buying to get a feel for how he takes care of things and his general personality; I believe him when he said he takes care of his stuff. I've also been over this truck with a fine toothed comb and he has kept up on EVERYTHING. That being said, it has 156,000mi and I can't really tell how old the O2 sensors are. There are no codes being thrown or anything (runs like a 1,000,000 bucks) but I know from experiance that doesn't always mean anything (my Focus ran like CRAP when the O2 started acting wonky and it never did throw a code).


Anyways, I know this thing will NEVER be a fuel sipping "green car" but I'd love to be able to get 14-15 under normal driving and 18-20 on the open road. I think those are reasonable goals but they are a far cry from where I am now. :bawl: Fortunately, we have a couple of small cars for daily driving that get 35-40mpg (saves me a TON o my 500mi/wk commute) but I LOVE driving the Expedition and would like to be able to drive it, in good concious that my kid's college money isn't going into my gastank, on the weekends and stuff.



Here's some thought I had on bringing that mpg number up:
1) electric fans to replace the mecanical one. I've had good success on previous vehicles in getting mpg's up by doing this, I see no reason why the Expy would'nt respond favorably to getting rid of that HUGE clutch fan.

2) I have a Flowmaster 50series muffler sitting in my garage. Given out "granny" driving style a full exhaust system seems like a bit of a waste but maybe there's some mpg to be had by getting rid of the trashcan muffler Ford put on there???

3) Tires are already aired up to 44psi (max sidewall pressure). They are already a mild "street" type tread so I just don't think there is any more to be had from that area.

4) headers? I see that Summit Racing has a set for $200. Since I have an exhaust leak to take care of anyway why not, right? Anyone have experiance with headers improving their MPG's? It sure couldn't hurt to get rid of those worthless logs Ford put on there I would think.

I appologize for the LONG post. My sincere thanks to anyone who managed to read through the entire thing.:favorites13: Any help or insight would be greatly appreciated.
 

tonydiv

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You're the second person in as many weeks who has decided to run their tires at pressures in the mid 40s. DON'T, it's not safe to run them at those high pressures. Correctly inflate them to the psi that is on the door tag.

Also, what little you are reducing in rolling resistance is made up for in drag to turn a tire that now has a slightly larger diameter.
 
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captain chaos

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You're the second person in as many weeks who has decided to run their tires at pressures in the mid 40s. DON'T, it's not safe to run them at those high pressures. Correctly inflate them to the psi that is on the door tag.

Also, what little you are reducing in rolling resistance is made up for in drag to turn a tire that now has a slightly larger diameter.

Thanks for the concern but running a tire at 44psi (that is rated for 44psi) is not at all a "safety concern". Running a tire rated for 35psi at 44 could very well lead to disaster though.
There might be a barely measureable amount of tread that is no longer in contact with the pavement due to the higher pressure, we're talking less than a 1/10 of an inch at the worst, but the difference in rolling resistance is MUCH more dramatic. Tires deform as they roll around and make contact with the road. This causes friction (rolling resistance) and heat. A tire inflated to a higher PSI will deform less for a given load; less friction, less heat, less rolling resistance. The biggest tradeoff to a higher tire pressure is the rougher ride. Also, a highly inflated tire will turn (side to side) MUCH easier than one with lower pressure. Don't believe me, lower your tires down to 15psi and try to turn the wheel (but don't drive on them because that IS a safety concern).
Running a tire at it's maximum advertised PSI (as per the sidewall information) is a VERY common way of squeeking out better mileage.
 

jacks3am

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I run at 44psi and im rated for it, for the last 6 months!
 

2000eb

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sorry tonydiv im runnin 44 for over a year i have always ran 40-44 normally 42-44 upfrpnt and 40 in back since more weight is in the front my parents run max tire pressure and got 70k miles out of a 40k tire but they drive alot nicer then i do
 

sgtowing

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The tire pressure is fine. The electric fans will help. Especially in the "but dyno dept". If you do the headers, get long tubes and do the whole exhaust. Expensive but worth it. You should think about getting a tuner for it. One that has a fuel economy setting. And last, a complete tune up. Cleaning the mass air meter as well.

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captain chaos

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The tire pressure is fine. The electric fans will help. Especially in the "but dyno dept". If you do the headers, get long tubes and do the whole exhaust. Expensive but worth it. You should think about getting a tuner for it. One that has a fuel economy setting. And last, a complete tune up. Cleaning the mass air meter as well.

Sent from my DROID BIONIC using Tapatalk


At my 2000rpm shift points my "butt dyno" is reading about 3 1/2hp. :Big Laugh:
Some more pulling power would be nice but gas mileage is my primary concern. I have a Hayabusa for when I want to tickle the "butt dyno".:burnout:

I may try a few simple, inexpensive things to start with. I have a couple electric fans sitting the in the garage as well as that Flowmaster. I've also already done the GOTTS mod to it. I'll have to see where that gets me.
I don't really want to sink a TON of money into a vehicle that might see 5000mi a year. I have 2 VERY cheap to drive commuter cars (as well as my bike) to take care of the daily driving duties and an old Mustang to suck up all of my spare cash. :biggrin:
 
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captain chaos

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WooHoo!
Just filled the truck back up. This time around it was 14.3mpg. This was all just "normal" running with no highway.
What I did since last time was remove the brush guard, remove the intake snorkel and close off the hole in the fender (forcing the truck to "breath" the warmer underhood air) and reset the computer. If my MPG's start creeping back down I'm going to look more into my "exhaust leak causing the O2 to sense a lean condition" theory.

I'm cautiously optimistic that I can achieve 15-16mpg with some more mods (electric fan/exhaust) and careful driving. That's not far off from what we got from the Jeep and the extra room has already proven itself to be AWESOME!
 

JUST4FUN

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you'll be crying big boy tears when you tow the camper, i tow a TT and get 8.5 with a 5.4
with the 4.6 it will probly be around 8 depending on the camper.
the expy is around 6000 lbs you will mabey get 15 out of it city and thats it, just the nature of the beast. mine gets 12.6 city and 18 highway and im happy
BTW follow the pvc hose too the back of the engine see it the part that connects to the manifold is collapsed this will be a vaccume leak replace it
 

JUST4FUN

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cold ait makes hp not warm air thats why the put intercoolers on turbos
you need a cold air intake (CAI)
 
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