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 Post subject: Low MPG in a 3.7 KJ
PostPosted: Sat Mar 24, 2012 9:47 am 
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Afternoon Gents

Please would you assist.

My 2003 KJ has 96000mi on the clock, she is currently giving me 11.7MPG, this is a mixture of town and highway driving, she seldom sees more than 2000rpm so i have a very light foot. I am sending her in for a major service next week, i recently purchassed the Jeep and dont think the the plugs have been changed in ages. The Cats are all fine.

What else can i look at to sort my MPG out...ive read that the MAP sensor can play a part in high MPG,if so please would you assist me in locating and cleaning this out............. please assist!

Thanks
Jayson
South Africa


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Wed May 02, 2012 7:58 pm 
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Wow...that is some poor mileage. Sure, new plugs will help and check air filter and really anything else replaceable in the anti-pollution system. Some KJs have mileage issues. Check out some other threads on this site concerning mileage. Good luck!

FYI: I am getting 21.5 mpg mixed city and highway

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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Wed May 02, 2012 8:24 pm 
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Jay4 wrote:
Afternoon Gents

Please would you assist.

My 2003 KJ has 96000mi on the clock, she is currently giving me 11.7MPG, this is a mixture of town and highway driving, she seldom sees more than 2000rpm so i have a very light foot. I am sending her in for a major service next week, i recently purchassed the Jeep and dont think the the plugs have been changed in ages. The Cats are all fine.

What else can i look at to sort my MPG out...ive read that the MAP sensor can play a part in high MPG,if so please would you assist me in locating and cleaning this out............. please assist!

Thanks
Jayson
South Africa

Believe it or not but in bold is the #1 cause of bad mpg's.Promotes massive carbon buildup in the intake which drastically reduce mpg's.Gotta get out and "clean the cobwebs out" at least once a week,IE drive like you stole it for at least 30-60mins once a week,does wonders.


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Thu May 03, 2012 3:04 am 
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Wow, I cant believe that, will def give it a go, many thanks!


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Wed Nov 28, 2012 2:36 pm 
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True story, alot of times you just need to get up on it, when i was in the Force we had F-350s that we would drive around the line, (never over 15 mph) and once a month we had to take them to the highway and drive them like a normal truck, not entirely what you were talking about but I actually had something to add to the conversation so I took my shot.

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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Sat Feb 23, 2013 12:06 am 
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In fact, alot of the issues with liberties dropping valve seats or having valves fail is due to the fact that Chrysler didn't design the valves to rotate as well as they should (which keeps the seat clean and the seal good, as well as keeping the valves appropriately lubed)

My xj gets 24-25mpg all day IF i stay in the "sweat spot". this is where the HP and Torque curve meet, right around 2250rpm on stock, but mine meets around 1850RPM with a torquer cam.

My KJ gets around 19mpg with 4.10 gears and 32" Hankook MT's, with mixed driving, hitting 2750RPM as much as possible.

Keep it lower, it gets worse.


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Sun Mar 17, 2013 2:43 pm 
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11mpg! :shock: I do almost 19 granny'in around. I dont see much difference cruising at 60mph or 75mph on the open road. Then again, I am bone stock.

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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Sun Mar 17, 2013 7:27 pm 
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stev0 wrote:
11mpg! :shock: I do almost 19 granny'in around. I dont see much difference cruising at 60mph or 75mph on the open road. Then again, I am bone stock.

I get 9mpg's city,but yeah far from stock.


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Mon Mar 18, 2013 9:02 pm 
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I noticed that traveling around 75 I would average around 16.7 mpg (evic readout). If I was going 65 I got 19.4. Mine has a 5 speed though (stock for now).


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Mon Mar 18, 2013 9:02 pm 
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I noticed that traveling around 75 I would average around 16.7 mpg (evic readout). If I was going 65 I got 19.4. Mine has a 5 speed though (stock for now).


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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Sun Jul 07, 2013 6:19 am 
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I've noticed that no matter what speed or engine rpm I maintain, my liberty is a gas hog. That's why I have an old honda civic with the smallest engine. Gotta love over 40mpg with no hybrid nonsense just small light cheap and stingy.

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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Mon Oct 14, 2013 12:39 am 
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I'm in ill annoy and in an attainment area so stuck with some of the most wretched ethanol diluted chemically contaminated EPA violated fuel in the country. My 2002 Limited (tall version before they lowered them) has never gotten better than 12MPG city. It used to get about 21 highway once we got out of the area and could get real gasoline. I do mostly city driving, not grannnying, but get out on the freeway at least every other week.

Over the years I've done plug replacement, K&N filter element, AMSoil filter element, exclusive use of Mobil-1 oil, cold air induction, Sea Foam treatment, 2.5" cat-back exhaust, various tire pressure variations, and replaced the tires. I've also pulled the back seat out (just flat storage back there now, and its generally empty). Nothing made city mileage go over 12MPG except getting real unadulterated gasoline (in which case I currently get 13.5 or so). Last highway trip was 18.5MPG but the states we drive through no longer have readily available non-ethanol gasoline.

At this point I've given up on trying to improve it. Just going to keep driving it until its time for a new vehicle.

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 Post subject: Re: Low MPG in a 3.7 KJ
PostPosted: Fri Jul 20, 2018 5:41 pm 
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If you want better MPG you need to ditch the 3.7 gas guzzler and get a 2.8 CRD instead, preferably one with a manual six speed gear box, like mine...I average 38mpg in mixed driving, dropping to around 33mpg with the Aircon on all the time. :wink:
PS, and mine is a 4x4!


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