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Discussion Starter · #1 ·
I'm new to forum so pardon any mistakes.

I've got a 2014 Wrangler Sport 3.6L V6 VVT basic package with P255/75R17 tires. Only have 20k miles and in the past 6 months I found myself stopping at the gas station weekly. I finally started tracking miles driven between fill ups and found I was getting about 6mpg in local driving. I'm supposed to get around 17mpg (which was what I was getting when I first bought the JK).

I went to Jeep dealer and they thought it was a bad rocker arm issue that previous models had and they replaced one that was ticking. The ticking went away but the mileage stayed the same. I brought it back and dealer found a update for the PCM regarding O2 sensors. They test drove it for about 100 miles in local and highway traffic and said it was getting 17-20 mpg. I picked the car up and they had filled my gas tank. I got gas yesterday and filled it up with 14.6 gals and had only traveled 75 miles since getting it back from the dealer.

Does anyone have any ideas what's going on because the dealer doesn't seem to have a clue?
 

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Discussion Starter · #3 ·
I first thought about that and bought a lock gas cap. That didn't solve my issue. Also forgot to mention my JK is an automatic.
 

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Not sure they would affect gas mileage much, but just throwing some ideas out there... Tire Pressure, Blocked Air Filter, Stuck Brake Caliper (or dragging Parking Brake), Bad Fuel Injector, Bad Spark Plug, or a possible a fuel leak.
 

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14.6 is low but in the ball park. Once they reset the PCM it takes some miles for the engine to dial in. Give it some time.
 

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14.6 is low but in the ball park. Once they reset the PCM it takes some miles for the engine to dial in. Give it some time.
OP said 14.6 gallons of gas to travel 75 miles (~5 MPG) (not trying to be rude, just helpful!!)
 

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14.6 is low but in the ball park. Once they reset the PCM it takes some miles for the engine to dial in. Give it some time.
he said he put 14.6 gallons of gas in after only 75 miles Yikes.... definitely something amiss.
 

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Have you verified your speedo is reading correctly ?since you bought the Jeep used, i wonder if its possible it's got the wrong tire size in the calibration, throwing off your mpg calculation ? if it had a leaking injector, fuel leak, bad spark plugs, bad o2 sensors etc, i'd imagine there will be indications of such of a thing in your dash with error codes all over the place.
 

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If you were really getting 5-6 mpg there would be drivabilty issues and / or fuel diluting your oil, I would think. That much fuel can't be running through your motor and you not notice something is wrong. I would think it is leaking, or otherwise exiting the Jeep. That is a lot of fuel for that little engine to burn.
 

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If you were really getting 5-6 mpg there would be drivabilty issues and / or fuel diluting your oil, I would think. That much fuel can't be running through your motor and you not notice something is wrong. I would think it is leaking, or otherwise exiting the Jeep. That is a lot of fuel for that little engine to burn.
This.

Do you smell fuel while you are driving? When you pull the oil dipstick out does it smell like fuel? Keeping pace with other vehicles in traffic is your speedometer off drastically?

If you don't smell fuel and calibration seems accurate, I'd guess at someone stealing fuel. You don't have to go through the gas cap to get fuel out.
 

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One thought though it is unlikely. It may not be entering closed loop for some reason. If you have the torque app you could check. My 2011 enters closed loop very soon after a cold start so I would expect yours to also do that. It is unlikely but possible. I would think it would throw a code though.
 

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Discussion Starter · #14 ·
The dealer tells me they've run the computer analysis. The only thing they got was to update the PCM. They said that fixed it but I'm not getting the same results. I just filled the tank yesterday; drove 107 miles and put in 15 gals. There are no visible leaks and the Jeep seems to perform ok. When I started it the other morning it did shut down abruptly. I restarted it and then it was fine.
 

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Discussion Starter · #16 ·
This.

Do you smell fuel while you are driving? When you pull the oil dipstick out does it smell like fuel? Keeping pace with other vehicles in traffic is your speedometer off drastically?

If you don't smell fuel and calibration seems accurate, I'd guess at someone stealing fuel. You don't have to go through the gas cap to get fuel out.
I have smelled fuel occasionally but just on start up in the morning which I assume is not unusual. If gas can be stolen without going through gas cap, how is that done?
 

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Discussion Starter · #17 ·
One thought though it is unlikely. It may not be entering closed loop for some reason. If you have the torque app you could check. My 2011 enters closed loop very soon after a cold start so I would expect yours to also do that. It is unlikely but possible. I would think it would throw a code though.
What does closed loop mean?
 

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Check your oil level, is it going up? Possibly getting fuel in the oil?

Another possibility is that the jeep is programed for larger tires and prior owner put little tires back on. Have you checked your speedo vs a GPS or speed app on your phone?
 

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Discussion Starter · #19 ·
Have you verified your speedo is reading correctly ?since you bought the Jeep used, i wonder if its possible it's got the wrong tire size in the calibration, throwing off your mpg calculation ? if it had a leaking injector, fuel leak, bad spark plugs, bad o2 sensors etc, i'd imagine there will be indications of such of a thing in your dash with error codes all over the place.
I bought the Jeep new from the dealer, I am the only owner. I can ask about the calibration of the speedo. I did do my own experiment where I measured the distance between point A & point B using the trip meter. I checked out the same using Google maps and I was within one tenth of a mile. Not sure if this is scientific enough.
 

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What does closed loop mean?
In closed loop your O2 sensors monitor the air fuel ratio to keep you at a precise air fuel ratio for optimum mpg and to keep epa happy. This is at cruise and low load driving under acceleration you go open loop giving more fuel ie might go 12 to 1 vs 14.7 to 1 ie run richer
 
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