Poor fuel mileage - 17 mpg average - STUMPED!!

altdiesel · **Posted:** Wed Sep 12, 2012 10:56 am

I can't figure out why my wife's 2006 Jeep Liberty is getting about 17.8 MPG hand calculated no matter how it is driven, on highway, or combination of city and highway. No CELL... This has been about the same for the last 7,000 miles. Tried lots of different fill up stations, so the fuel factor has been eliminated. Here is a list of all the new parts, and all the frustrations that come along with not seeing results!!!

I have taken it to 2 independent diesel shops here in Colorado Springs, and even the dealer, and they all can't do anything without a code to read. I am about to unload it and jump for the regular ol gas and get the same fuel mileage!! Please help!

about 82,000 miles right now

*New Fuel Heater Head
*Samco Hoses
*Full Torque GDE tune (BTW, Keith is awesome to work with!!)
*New OEM thermostat (my engine still does not warm up to 180 degrees, seems stuck at 168 with a/c off, with a/c on it will get to 193)
*Running 10w40 Mobile 1
*New torque converter - Precision of Hampton ( it's what the transmission shop I took it to uses) http://www.gopnh.com/Automotive-Part-Number.cfm
*New transmission pump (it would not engage in R or D after hot soaking)
* in tank fuel pump ( Cummins lift pump that Sam recommended from RockAuto)

Dennis MacGyver · **Posted:** Wed Sep 12, 2012 12:13 pm

Only been on this forum for 2 months, and quite frankly I am astonished at the high level of variability of fuel mileage people have with this vehicle.
We've only owned our '06 for 2 months now, and on average I'd say we're getting about 26 mpg overall. We've installed the GDE Eco tune, a Ram TCM, and rewired the AC to only come on when you push the AC button. Put in a Provent, AFE "7" air filter, took off the boat anchor off the rear diff, we leave the spare tire at home.
We accelerate VERY carefully keeping the rpm's under 2000 and in 5th lock-up we drive at 1800 rpms.

My 1st "guess" at your situation would be your right foot. If your accelerating up to speed quickly, you are going to kill your mileage. To accelerate slowly is a huge pain since this little Liberty pony wants to "jump" off the line. It takes a lot of right foot training and a bunch of disregard, to the vehicles behind you, to stay true to the cause of high mileage.

audiboy86 · **Posted:** Wed Sep 12, 2012 12:27 pm

Map sensor and air filter would be my first two things I would look at and then my exhaust system somewhere you not getting enough of something.

spitfire36o · **Posted:** Wed Sep 12, 2012 12:49 pm

check for sticking brake calipers, check for worn wheel hubs/bearings, remove and carefully inspect the intercooler hoses, check the intercooler for cracks as well.

jkbkwarner · **Posted:** Wed Sep 12, 2012 1:25 pm

It almost sounds like you're not getting to OD? Are you even using 1st gear? I've had an intermittent problem where I would start off in 2nd gear and go to 3rd but it wouldn't get to 4th or overdrive. I would drive at 65mph, but my rpm was over 3K.

papaindigo · **Posted:** Wed Sep 12, 2012 2:57 pm

Quick RPM check for proper top gear is easy. 1800rpm on the highway puts you right about 62mph regardless of transmission "tuning" although if you have the F37 transmission tune you may have to run your speed upto ca. 65mph to get into top gear/OD and then drop back to 62mph or so to check rpm.

Big Montana · **Posted:** Wed Sep 12, 2012 5:10 pm

I like the idea of checking the RPMs at a certain speed. I get at least 22 mpg in deep winter and ALL short drives to work.

I'm troubled by the temp of your Jeep. I changed my thermo out years ago because it wasn't getting warm enough, and I would say I realized a 1-2 mpg improvement.

What about tires? What about ride quality? Do you have any noises or pulls in the drive? I'm pretty sure that I have a bad wheel bearing starting this week and that seems to be taking me down a bit in millage.

Does Keith have any ideas? I've only had the full torque tune for one full tank of fuel, so I'm not sure how my mileage will change from two+ years on the regular ECO tune the the FT tune.

Give us more to know about your Jeep. Smoke? anything else?

ATXKJ · **Posted:** Wed Sep 12, 2012 8:26 pm

spitfire36o wrote:

check for sticking brake calipers.

x2 - this is a problem with all Liberties

striperman36 · **Posted:** Thu Sep 13, 2012 9:49 am

x3

take off one of the boots, cram it with lube grease and put it back on. Happened to me on 1 front and 1 rear caliper.

Your rims should be very hot if you are draggin and you can warp you rotors, they could be tinted by the overheating.

You should be able to smell brake when you stop and sniff around the wheel.

None of these should happen if you are not draggin.

dirtmover · **Posted:** Thu Sep 13, 2012 10:38 am

Calipers was my first thought also but after 7000 miles I'd think his question would be "Why are my brakes making a grinding noise?"

I'd start with the temperature since it clearly appears to be low.

How are you validating this? If you're using the gauge then be aware that there are 2 variations out there depending on model and ECU version. If you're using the wrong picture to interpret 180 = 168.

Maybe your fan stuck is on and you're over-cooling?

I saw almost exactly a 10% mpg hit due to a bad stat. Maybe your new one is also bad?

altdiesel · **Posted:** Thu Sep 13, 2012 3:00 pm

dirtmover wrote:

Calipers was my first thought also but after 7000 miles I'd think his question would be "Why are my brakes making a grinding noise?"

I'd start with the temperature since it clearly appears to be low.

How are you validating this? If you're using the gauge then be aware that there are 2 variations out there depending on model and ECU version. If you're using the wrong picture to interpret 180 = 168.

Maybe your fan stuck is on and you're over-cooling?

I saw almost exactly a 10% mpg hit due to a bad stat. Maybe your new one is also bad?

Nope, no brake problems. After driving the wheels are still cool to the touch. I am using an ECU reader called Torque Pro off of my Android phone. That is where I am getting the temp reading.

No excessive smoke. Keith did recommend to check the calipers dragging, not the problem. He also suggested to check the thermostat, which is why I replaced it.

mngoat01 · **Joined:** Wed Aug 06, 2008 11:25 am **Posts:** 67

what where you getting for fuel mileage before the change?

naturist · **Posted:** Thu Sep 13, 2012 7:39 pm

17 is indeed low. Have you checked that the odo is reading correctly? if you've put oversize tires on it, and not recalibrated the odo, it would read fewer miles than actually traveled.

Have you noticed everywhere is always uphill and into the wind?

Fuel leak, maybe?

Do you have a practical joker neighbor who's been stealing a couple gallons every night?

The experts say that from the best mileage driving habits to the worst, there is about 1/3 drop in vehicle performance with any vehicle. You are over that, I'd say. There is certainly something odd going on.

ATXKJ · **Posted:** Thu Sep 13, 2012 7:54 pm

I've got 265/75/16 and I get 20+ in uncorrected odometer miles/ pumped gallons
and better mileage when I'm up in Colorado....

Well - you've checked everything obvious and several non-obvious

How does that torque converter feel? - does it lock up well? does it feel like it's slipping?
any way to check tranny oil temps?

DOC4444 · **Posted:** Thu Sep 13, 2012 8:01 pm

Given all the rule outs, I' m leaning towards odo error. Check against GPS and report. Have you figured out how to get Torque to display oil temp, pressure and trans temp?

DOC

altdiesel · **Posted:** Fri Sep 14, 2012 4:52 pm

DOC4444 wrote:

Given all the rule outs, I' m leaning towards odo error. Check against GPS and report. Have you figured out how to get Torque to display oil temp, pressure and trans temp?

DOC

Torque Pro will not display oil temp, pressure or trans temp, I wish it would. One very odd thing that is not fuel economy related, is when I have it scanned with a Star Mobile Dodge scanner, it does not communicate with the BCM. I also get a Steering angle low voltage sensor error, only stored code in the whole thing.

I will check my tire sizes to see if they are indeed oversize over stock. They where the tires that where practically brand new when I bought the vehicle the PO put on.

Doing the Full Torque GDE tune did not help with fuel mileage at all. Seems like it is a bit quicker. Smokes a little more black smoke.

Bottom line, it feels like it has lots of power, and my wife loves to drive it. I just wish it got what everyone else seems to get.

Oh, and trust me, my wife babies the gas pedal, she is *Trying very hard to drive it easy to get better fuel mileage. No lead foot there.

Dennis MacGyver · **Posted:** Fri Sep 14, 2012 4:58 pm

altdiesel wrote:

DOC4444 wrote:

Given all the rule outs, I' m leaning towards odo error. Check against GPS and report. Have you figured out how to get Torque to display oil temp, pressure and trans temp?

DOC

I will check my tire sizes to see if they are indeed oversize over stock. They where the tires that where practically brand new when I bought the vehicle the PO put on.

My factory new spare tire, measures 29.5" high

DOC4444 · **Posted:** Fri Sep 14, 2012 9:21 pm

I guarantee something is wrong if you added ANY GDE tune and you have not seen an significant improvement in fuel mileage. It is typical to see at least 3-4 MPG more, unless you are using all the extra power, which you say you are not.

It is NOT normal to see MORE smoke with either of the ECO tunes. They are virtually smoke free.

So, if you are making black smoke, excess fuel is going out the tailpipe and killing your mileage.

Check with Keith as to what things to go through to pinpoint the cause of the overfueling.

Don't give up.

DOC

altdiesel · **Posted:** Fri Sep 14, 2012 11:18 pm

Dennis MacGyver wrote:

altdiesel wrote:

DOC4444 wrote:

Given all the rule outs, I' m leaning towards odo error. Check against GPS and report. Have you figured out how to get Torque to display oil temp, pressure and trans temp?

DOC

I will check my tire sizes to see if they are indeed oversize over stock. They where the tires that where practically brand new when I bought the vehicle the PO put on.

My factory new spare tire, measures 29.5" high

So after my wife got home from work, I checked the tire size and what is on the jeep now is 235x70r16, this is actually smaller than what is stock. So, my fuel mileage is actually worse than what I thought...

Weird update, after my wife got home, she drove off (after the Jeep sat for maybe 45 min), and it started shuddering really bad, to the point where it shut off. I am going to bring it over to my buddys shop and have him scan it hopefully with a stored code. There was no check engine light that went off, btw...

Stock Tire - 225/75R16 Search Tires Tire 1 - 235/70R16 Search Tires
Section Width: 8.85 in 225 mm
Section Width: 9.25 in 235 mm My tire..
Rim Diameter: 16 in 406.4 mm
Rim Diameter: 16 in 406.4 mm
Rim Width Range: 6 - 7 in
Rim Width Range: 6 - 7.5 in
Overall Diameter: 29.28 in 743.71 mm
Overall Diameter: 28.95 in 735.33 mm My tire is .33 inches smaller, not that much smaller, just wider...
Sidewall Height: 6.64 in 168.65 mm
Sidewall Height: 6.47 in 164.33 mm
Radius: 14.64 in 371.85 mm
Radius: 14.47 in 367.53 mm
Circumference: 91.98 in 2336.2 mm
Circumference: 90.94 in 2309.8 mm
Revs per Mile: 710.3
Revs per Mile: 718.4
Actual Speed: 60 mph 100 km/h
Speedometer1: 60.6 mph 101. km/h

WolverineFW · **Posted:** Sat Sep 15, 2012 12:29 am

DOC4444 wrote:

I guarantee something is wrong if you added ANY GDE tune and you have not seen an significant improvement in fuel mileage. It is typical to see at least 3-4 MPG more, unless you are using all the extra power, which you say you are not.

It is NOT normal to see MORE smoke with either of the ECO tunes. They are virtually smoke free.

So, if you are making black smoke, excess fuel is going out the tailpipe and killing your mileage.

Check with Keith as to what things to go through to pinpoint the cause of the overfueling.

Don't give up.

DOC

Agreed....ECO tune should not smoke. My jeep smoked on hard throttle with the stock program. No smoke at all with the ECO tune. Have you had your injectors tested to see if they are functioning correctly? Definitely too much fuel if you are smoking.

Poor fuel mileage - 17 mpg average - STUMPED!!

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