03 4.6 BAD MPG... NO CODES?

[Smear]

Hi all! I am a new member, so forgive me if I mess up on making this thread. I have had this problem with my 03 Explorer (150k) for a good 5 months now (since I got it). It is a RWD and has a 4.6 and the 3.73 LS axle. I've been getting pretty bad gas mileage, about 9-12 mpg. No CEL and no fluids on the ground after I park it. It does not idle roughly. The plugs were changed 2-3 years ago. Replaced thermostat and performed coolant flush (heat was not working well, warmed up very slow and heard a bad thermostat reduces gas mileage) and cleaned my air filter. Also performed an oil change and put a new serpentine belt in (old one worn). Warms up quickly and heat works now, but gas mileage still bad. I use my Ex as a commuter in my town, but my commute is mostly highway at 55 mph. I am getting around 220 miles to my 22.5 gal tank. Previous owner (and relative) said he used to get a good 300 out of the tank. I do not tow or carry anything and I don't floor it often. There's an occasional loud 2 second rattle on cold start which has already been diagnosed as a cat shield. There's also a burning smell (especially after I've run it hard), but I think that's just oil burning somewhere on the manifold. My first oil change I did on it, it was missing a tiny amount of oil so no surprise. I've also noticed my muffler has a few small cracks in it, maybe something to do with back pressure? Maybe this kind of mpg is normal with the V8? Are you guys having this kind of mpg as well? Our '13 F150 with a 5.0 gets about 16 mpg, so this kind of mileage is a bit unusual to me even for a V8. I do have a slight vibration at idle when the the truck is in drive, and I do have the notorious lunging transmission. Lunging only occurs when I'm shifting into Drive or Reverse and when i let off the gas after getting on it, maybe torque converter lockup issue? Looking forward to your responses!

 

[fordysenior]

Mine is an early build 2002 with the 3.73, 4.6L and four wheel drive with about 130k. It's been eating a little oil for awhile now, but still runs like a champ. My gas mileage is around 16 mpg and 300 miles a tank. It's been a very good vehicle, so I don't have any info to help you with yours -- just answering your question on what might be normal for these.

 

[Smear]

Mine is an early build 2002 with the 3.73, 4.6L and four wheel drive with about 130k. It's been eating a little oil for awhile now, but still runs like a champ. My gas mileage is around 16 mpg and 300 miles a tank. It's been a very good vehicle, so I don't have any info to help you with yours -- just answering your question on what might be normal for these.

Thanks for the info! That means something's definitely wrong with my mileage lol!

 

[lincolnshibuya]

you need a scanner and take a look at your fuel trims, that indicates if the system is trying to add more fuel. A positive trim above 10 will cause bad gas mileage.

 

[Smear]

you need a scanner and take a look at your fuel trims, that indicates if the system is trying to add more fuel. A positive trim above 10 will cause bad gas mileage.

I've seen a guy on youtube do this and found a vacuum leak. Where can I get a scanner? Is it like an OBDII scanner? Sorry about all the questions. I appreciate your response!

 

[fordysenior]

One option is to go to Amazon.com and input ELM 327 -- it will show you connectors for connecting to your computer. Then you download Forscan onto your pc. As for me, I'm old school, never learned how to use these scanners, but you can read codes without much effort. And I haven't taken time to learn yet, but I have two good running fords so I haven't needed it much yet. And it's an inexpensive way to go.

 

[Smear]

One option is to go to Amazon.com and input ELM 327 -- it will show you connectors for connecting to your computer. Then you download Forscan onto your pc. As for me, I'm old school, never learned how to use these scanners, but you can read codes without much effort. And I haven't taken time to learn yet, but I have two good running fords so I haven't needed it much yet. And it's an inexpensive way to go.

Appreciate it fordysenior! I'll contact a tuning friend of mine as he has these kinds of programs on his PC. He should be able to run fuel trim data. Thanks for your help!

 

[IIGood]

I am getting around 220 miles to my 22.5 gal tank.

Okay...first, how much fuel do you ACTUALLY fill the tank with when you refuel? I'd pay attention to that, because I doubt you're using all 22.5 gallons each time you fill...so first determining the actual mileage is key here.

I have a V6 in my XLT and I'll get between 17-20 mpg depending on the type of driving. It does a lot of longer distance runs so it'll mostly be towards the higher end of that range...but again, that's a V6. I'm not always filling up when the needle is on "E"...I'm usually putting between 18 and 20 gallons in the tank at fill-up.

I also have a Mustang GT which has the 4.6L V8 in it. I'll typically get about 20 mpg out of that on everyday city/highway driving. But, again, that's in a Mustang...a vehicle that weighs about 1500 lbs less than the Explorer. And it's a manual transmission.

 

[Mbrooks420]

I’m doubting the 2 second rattle is the heat shields, I’d be much more inclined to think it’s your timing tensioners. If your wires are 2-3 years old, and aren’t factory, or a very quality brand they are probably due again.

 

[J_C]

^ Agreed, a heat shield rattle will tend to continue sitting there idling and to rule it out one can merely wrap some solid core, uninsulated wire around it a few times and twist it tight, though also look at the heat shields on the pipes and muffler and for broken exhaust hangers.

I've also noticed my muffler has a few small cracks in it, maybe something to do with back pressure?

I suppose there's a slim chance the internal baffling is loose and rattles... seems like a two person job, one starting it while another is under the vehicle trying to locate the noise.

 

[Smear]

I’m doubting the 2 second rattle is the heat shields, I’d be much more inclined to think it’s your timing tensioners. If your wires are 2-3 years old, and aren’t factory, or a very quality brand they are probably due again.

Man I'm scared if the rattle is the tensioners. I haven't checked the wires, but wouldn't it throw a code? Had a friend of mine say it might be O2 sensors (sometimes don't trip a CEL) or a vacuum leak. I'll bring it in to a trusted mechanic soon. Update: got a pathetic 220 miles out of my tank. Same gas station since before I had the problem. Thanks

 

[Smear]

Okay...first, how much fuel do you ACTUALLY fill the tank with when you refuel? I'd pay attention to that, because I doubt you're using all 22.5 gallons each time you fill...so first determining the actual mileage is key here.

I have a V6 in my XLT and I'll get between 17-20 mpg depending on the type of driving. It does a lot of longer distance runs so it'll mostly be towards the higher end of that range...but again, that's a V6. I'm not always filling up when the needle is on "E"...I'm usually putting between 18 and 20 gallons in the tank at fill-up.

I also have a Mustang GT which has the 4.6L V8 in it. I'll typically get about 20 mpg out of that on everyday city/highway driving. But, again, that's in a Mustang...a vehicle that weighs about 1500 lbs less than the Explorer. And it's a manual transmission.

Hi IIGood. I did a couple run-to-near-empty runs just to make sure I got the most I could. I ended up filling about 19-20 gallons. After it fills, I reset the trip meter. My last trip meter readings ranged from 210-240 miles, averaging about 230. Very low for the 14 City rating. As I said before, I take mostly 60mph highways on my commute (roughly 7 mile drive). My city is flat, no hills to climb. Weather out ranges from 30s in the morning to 60s in the afternoon.

 

[Smear]

Also heard clogged cats might decrease mileage? but without a code too?

 

[J_C]

As I said before, I take mostly 60mph highways on my commute (roughly 7 mile drive).

You're barely getting it warmed up from 7 minutes running. This might be worst case scenario and everything is fine, but do hook up a scanner and look at live fuel trim data.

 

[Smear]

Also heard clogged cats might decrease mileage? but without a code too?

You're barely getting it warmed up from 7 minutes running. This might be worst case scenario and everything is fine, but do hook up a scanner and look at live fuel trim data.

There are stoplights, so my overall trip lasts about 15 minutes. I live deep down in my neighborhood. It takes a good 4 or 5 minutes minutes to get out of. I never go over 35 mph in my neighborhood, and she's up to operating temperature by the time I hit the highway. I'm planning on hooking up a scanner soon. For now, I'm letting her sit a bit more and taking her out less often. Good excuse to put on some much needed miles on my leased car anyway.

 

[Mbrooks420]

Miles per tank is irrelevant. Monitor what you put in and calculate off of the trip meter and get an actual MPG reading.

 

[Smear]

Miles per tank is irrelevant. Monitor what you put in and calculate off of the trip meter and get an actual MPG reading.

I haven't even found an MPG meter in my car. I measure by dividing the distance travelled by my full tank capacity.

 

[Mbrooks420]

That’s not a valid reading of anything. Divide miles traveled by gallons pumped into the tank.

 

[Smear]

That’s not a valid reading of anything. Divide miles traveled by gallons pumped into the tank.

I will make sure to do that next trip to the pump. Thanks Mbrooks!

 

[J_C]

There are stoplights, so my overall trip lasts about 15 minutes. I live deep down in my neighborhood. It takes a good 4 or 5 minutes minutes to get out of. I never go over 35 mph in my neighborhood, and she's up to operating temperature by the time I hit the highway. I'm planning on hooking up a scanner soon. For now, I'm letting her sit a bit more and taking her out less often. Good excuse to put on some much needed miles on my leased car anyway.

It could be a combination of factors, one being how you're calculating MPG but also the slow speed stop and go till you get to the highway. Other things that can reduce real MPG are low tire inflation, heavier and/or aggressive terrain tread tires, or larger than stock diameter tires which can reduce apparent MPG by the vehicle traveling further than the odometer indicates, though these latter tire factors would have been present with the prior owner's reported MPG if you haven't changed tires, except he could have factored for a diameter difference in a MPG calculation.

Suppose you're only putting in 19 gallons at a fillup, that puts you at 220/19 = 11.6MPG. Suppose stop and go and neighborhood travel takes it down to 10MPG 1/3rd if your commute time, but it still takes 10 minutes to go 7 miles so your expected MPG could drop to around 15MPG. That is consistent with owner reports with the V8 on sites like this:
Gas Mileage of 2003 Ford Explorer

Tire differences could knock another 1-2MPG off that, old O2 sensors maybe another 1MPG, and this could bring it down to 12-13MPG which isn't far off from 11.6MPG. You mentioned you "cleaned" your air filter. Is it one of those oiled types that maybe fouls the MAF sensor or the MAF sensor just needs cleaned anyway?

It still seems like there might be a couple MPG missing somewhere, which is where getting the fuel trims to see if it's running rich come in if none of the above are issues, or if there's an intermittent misfire, not enough to set a code (maybe pending code?).