Loss of MPG / Power...any advice? - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 9 Old 07-30-2014, 06:48 AM Thread Starter
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Loss of MPG / Power...any advice?

This is my first post so I'm not entirely sure that I'm posting in the correct spot. Anyways, I have a 07 X with 64k miles, 2.5 lift and 33's.

After I first got the 33s put on, I went down to a Jeep event. Was getting 19.1 MPG on the way there (two hour drive. Usually, around town I averaged 17.8 ish). On the offroad course, the dude in front of me gets stuck pretty deep and needs to be pulled out. Afterwards, one of the guys working the event tells me to punch it to make sure I don't get stuck in the hole. I do exactly that. Hit it pretty hard. Could I have messed something up there? I noticed a big drop in MPG (in my mind) and loss of power on the way home. At first I thought it was probably because alignment was off and the Jeep was full of mud. 9 months later I'm averaging 16.4. 16.8 on long trips. I'm in FL, so the terrain is pretty flat, but any type of incline on the highway and I lose speed.

Basic stuff I've done so far: air filter, spark plugs and wires, alignment, throttle body, oil (sea-foam before hand).

My car knowledge is pretty limited, but if you all have any advice at all them I'm willing to listen. I understand bigger tires, lift, and wind can bring down the MPG (and the fact that it's a Jeep), but I was getting 19.1 before with the same setup I have now....and that was nice.

Edit: Would be probably good to add that I took it to Jeep and they pulled the codes and couldn't find anything wrong....not really sure they actually did any kind of inspection other than trying to pull codes.

Last edited by dallas_; 07-30-2014 at 07:10 AM.
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post #2 of 9 Old 07-30-2014, 08:57 AM
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Check your exhaust system... If you "clamped" the pipe down to where there is little room for for the gasses to flow it WOULD kill your power and MPG. Look all the way from the headers to the tailpipe.

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post #3 of 9 Old 07-30-2014, 01:30 PM
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Quote:
Originally Posted by dallas_ View Post
This is my first post so I'm not entirely sure that I'm posting in the correct spot. Anyways, I have a 07 X with 64k miles, 2.5 lift and 33's.

After I first got the 33s put on, I went down to a Jeep event. Was getting 19.1 MPG on the way there (two hour drive. Usually, around town I averaged 17.8 ish). On the offroad course, the dude in front of me gets stuck pretty deep and needs to be pulled out. Afterwards, one of the guys working the event tells me to punch it to make sure I don't get stuck in the hole. I do exactly that. Hit it pretty hard. Could I have messed something up there? I noticed a big drop in MPG (in my mind) and loss of power on the way home. At first I thought it was probably because alignment was off and the Jeep was full of mud. 9 months later I'm averaging 16.4. 16.8 on long trips. I'm in FL, so the terrain is pretty flat, but any type of incline on the highway and I lose speed.

Basic stuff I've done so far: air filter, spark plugs and wires, alignment, throttle body, oil (sea-foam before hand).

My car knowledge is pretty limited, but if you all have any advice at all them I'm willing to listen. I understand bigger tires, lift, and wind can bring down the MPG (and the fact that it's a Jeep), but I was getting 19.1 before with the same setup I have now....and that was nice.

Edit: Would be probably good to add that I took it to Jeep and they pulled the codes and couldn't find anything wrong....not really sure they actually did any kind of inspection other than trying to pull codes.
Holy hot break pads! my '07 with 29in tires and no lift gets 13MPG on a good day in town and ive not even hit 70k miles!
X2 on the headers/exhaust system

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post #4 of 9 Old 07-30-2014, 02:01 PM
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are you going by the computer in the dash or hand calculating it? the dash is very inaccurate.

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post #5 of 9 Old 07-30-2014, 02:38 PM Thread Starter
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Quote:
Originally Posted by Sick13JKUR View Post
Check your exhaust system... If you "clamped" the pipe down to where there is little room for for the gasses to flow it WOULD kill your power and MPG. Look all the way from the headers to the tailpipe.
I took a look once I got off work, but nothing stood out to me. Might take it to a shop and see if they can help.

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Originally Posted by LoneJK View Post
Holy hot break pads! my '07 with 29in tires and no lift gets 13MPG on a good day in town and ive not even hit 70k miles!
X2 on the headers/exhaust system
13MPG? Are you flooring it the entire time?!

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Originally Posted by leman View Post
are you going by the computer in the dash or hand calculating it? the dash is very inaccurate.
Hand calculating it.

Thanks for the replies, folks.
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post #6 of 9 Old 07-30-2014, 05:43 PM
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Originally Posted by dallas_ View Post



13MPG? Are you flooring it the entire time?!

Nope, hilly town... automatic 4.10 gearing with 29inch tires is more of a recipe for power, not fuel economy xD

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Last edited by LoneJK; 07-30-2014 at 05:46 PM.
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post #7 of 9 Old 07-30-2014, 08:11 PM
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Is it possible that one of your brake calipers has seized or is not releasing entirely? Try jacking-up one axle at a time and check to see if any of the wheels are not turning freely, or if you hear any scraping noise.

And, BTW, I would kill for 19MPG. Even 15MPG. Going up and down hills and mountains (at least what passes for Mountains in my area), stopping for traffic lights almost every quarter mile, and having to floor the gas pedal to get my anemic 3.8L spinning fast enough to pass slow traffic on the highways, I'm lucky if I can stay above 13MPG.

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post #8 of 9 Old 07-31-2014, 07:17 AM
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This may sound dumb, but did you fill up with gas before you headed home? Although E10 gasoline CAN contain up to 10% ethanol, most terminals blend it a lower percentage to make sure it's not over 10% when delivered to retailers. That's the litigious scoiety we live in. Some stations occasionally get loads with the full 10% ethanol blend, and that can definitely cause your Jeep to run differently. I've experienced a very similar drop in power and mpg with my Jeep after filling up with gas from a out of town station. If you did fill up before driving home, have you run that gas out yet?

Also, you stated the guy in front of you got stuck, so I assume you were driving thru mud? I had a Honda CRF that once lost power in a similar manner after literally plowing thru a really nasty mudhole. Turned out the gas tank vent/breather tube got clogged up. Once that was cleaned out she ran fine. Don't know if the JK has anything similar for the fuel system, but maybe someone one this site will know if that could be your gremlin.

Good luck.

BTW, my in town driving is stop and go almost every block the entire 3 miles to work. Rarely do I ever get over 35 mph in town. I get 12mpg city, 17 on the road with very similar set up as your Jeep.

Last edited by soonerfan85; 07-31-2014 at 07:21 AM.
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post #9 of 9 Old 07-31-2014, 08:07 AM Thread Starter
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Quote:
Originally Posted by BumpInTheRoad View Post
Is it possible that one of your brake calipers has seized or is not releasing entirely? Try jacking-up one axle at a time and check to see if any of the wheels are not turning freely, or if you hear any scraping noise.

And, BTW, I would kill for 19MPG. Even 15MPG. Going up and down hills and mountains (at least what passes for Mountains in my area), stopping for traffic lights almost every quarter mile, and having to floor the gas pedal to get my anemic 3.8L spinning fast enough to pass slow traffic on the highways, I'm lucky if I can stay above 13MPG.
Took it to a shop, they said they don't see any problems with the exhaust. I'll try to check the calipers tonight when I get home.
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