ZJ Gas Mileage Plummeting. HELP! - JeepForum.com
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post #1 of 16 Old 12-12-2012, 07:09 PM Thread Starter
BRae_in_a_ZJ
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ZJ Gas Mileage Plummeting. HELP!

97 5.2 with full time 4wd, 132k, stock gears w/ 32's

In chronological order: drove away on day one with 12.3 mpg.

Its been beat up since then (not worth explaining), fixed countless odds and ends/lots of maintenance, tranny slipped from second to third/grind with too much gas in second. drove like that for a while with 11.3 mpg

did a tv cable adjustment, now the only tranny issue is it goes all the way up to 2250-2300 rpms in first then shifts firm into second. after that its butter smooth. I replaced air filter, pvc valve, spark plugs, seafoamed, and new serpentine belt. after driving for a week with the above things listed i am getting 10.7 mpg.

Car is well maintained, i drive at an average pace. im not out racing around but i dont drive like grandma either.

Ive heard it could be the exhaust o2 sensors. but thats just a possibility. What are some other things i can do to improve my gas mileage?
thoughts and ideas would be greatly appreciated!


'97 5.2 Laredo "Maggie"
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post #2 of 16 Old 12-12-2012, 07:26 PM
Freestyle713
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Part of it is probably the winter fuel mix.

94 Grand Cherokee 5.2 33in. Federal Couragia M/T's on Procomp Steelies, np231 swap, IRO Hack n Tap SYE, Carolina Driveshaft, 4.5 in. lift, RE front upper/rear lower ca's, RC front lowers, Ironman rear uppers, IRO 4.5 coils in rear, 3.5 and 2" bb (no isolators) in front, Bilstein 5100's, Clayton/JKS adj. track bars, KOR rad support and SS, Magnaflow/Flowmaster exhaust, clear corners, custom light bar w/ Hella 500's

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post #3 of 16 Old 12-12-2012, 07:34 PM Thread Starter
BRae_in_a_ZJ
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Quote:
Originally Posted by Freestyle713 View Post
Part of it is probably the winter fuel mix.
I read that on here. Is that known as a significant difference?

'97 5.2 Laredo "Maggie"
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post #4 of 16 Old 12-12-2012, 07:39 PM
Freestyle713
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Quote:
Originally Posted by BRae_in_a_ZJ View Post
I read that on here. Is that known as a significant difference?
I know it's made a difference in my dads truck. Last winter he was getting about 6, in the summer it was getting about 7.

94 Grand Cherokee 5.2 33in. Federal Couragia M/T's on Procomp Steelies, np231 swap, IRO Hack n Tap SYE, Carolina Driveshaft, 4.5 in. lift, RE front upper/rear lower ca's, RC front lowers, Ironman rear uppers, IRO 4.5 coils in rear, 3.5 and 2" bb (no isolators) in front, Bilstein 5100's, Clayton/JKS adj. track bars, KOR rad support and SS, Magnaflow/Flowmaster exhaust, clear corners, custom light bar w/ Hella 500's

Quote:
Originally Posted by elcorvino View Post
Yea... It's kind of like the fat chick who lives around the corner. You aren't trying to get caught with her, but you know she'd be a good time.
Quote:
Originally Posted by ScottD16 View Post
I had a dream my entire family was attacked by a giant polar bear. The crazy part was he attacked us with a giant spoon. Best dream ever.
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post #5 of 16 Old 12-12-2012, 07:42 PM Thread Starter
BRae_in_a_ZJ
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Quote:
Originally Posted by Freestyle713 View Post
I know it's made a difference in my dads truck. Last winter he was getting about 6, in the summer it was getting about 7.
thats about a 15% difference. which means im actually doing well on the winter fuel if thats my issue. which after further reading it probably is...
thanks for the reply man

'97 5.2 Laredo "Maggie"
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post #6 of 16 Old 12-14-2012, 11:08 AM
BigClay
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Are you hand calculating or going off the VIC?

Current: 98 TJ, 33" TSLs
Past: 94 ZJ, built for the rocks
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post #7 of 16 Old 12-15-2012, 12:08 PM
ratmonkey
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winter fuel, and long times in open loop mode while warming up....usually sets me back about 2mpg on the grand, the car sees about 3mpg.

'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

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post #8 of 16 Old 12-16-2012, 06:31 PM Thread Starter
BRae_in_a_ZJ
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Originally Posted by ratmonkey View Post
winter fuel, and long times in open loop mode while warming up....usually sets me back about 2mpg on the grand, the car sees about 3mpg.
Thanks for your input. i also figured out that i get poor mileage because most of my driving is around town in NOVA traffic... fml. but i took a trip out to Berryville and acheived 12.5 that day on the highway there and back (with winter gas, and 32's)

'97 5.2 Laredo "Maggie"
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post #9 of 16 Old 12-16-2012, 06:37 PM Thread Starter
BRae_in_a_ZJ
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Quote:
Originally Posted by BigClay View Post
Are you hand calculating or going off the VIC?
My vic is dead but the overhead console tells me. is that reliable?

'97 5.2 Laredo "Maggie"
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post #10 of 16 Old 12-17-2012, 05:09 AM
ratmonkey
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No, not always.
Mine is, but most people find its off to some degree.

'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

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post #11 of 16 Old 12-17-2012, 12:55 PM
BigClay
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Quote:
Originally Posted by BRae_in_a_ZJ View Post
My vic is dead but the overhead console tells me. is that reliable?
I would do it by hand a couple times and see if the overhead is telling the truth.

Current: 98 TJ, 33" TSLs
Past: 94 ZJ, built for the rocks
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post #12 of 16 Old 01-06-2013, 07:41 PM
Muaymendez
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Tire size as well as tire inflation, Rear end lubrication, Winter fuel mixture,New air filet may be of different brand and not allowing as much air.
Seafoam could have also loosened something causing an injector not to flow correctly
I would check the tires and account for fuel mixture as well.
My motorcycle gets 40 in the summer and 36 to 38 in the winter.
Don't go by overhead reading especially if you changed tire size. All terrains as opposed to regular road tires will use more fuel
Air up fuel up, drive safe and be happy shes running well.
Not to be an *** but did you get a jeep for fuel economy?
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post #13 of 16 Old 01-06-2013, 08:01 PM
dnuccio
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ive heard that the overhead actually reads high most of the time

Reliability is relative
R.I.P. Ratmonkey
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post #14 of 16 Old 01-06-2013, 08:13 PM
dunkeye11
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Mine is a 96 all stock I got a 17.5 average on my 852 mile trip to Columbus Ga from NOVA
I had very bad mileage in nova but it is better here with less stops and a more common speed limit around 55 so maybe that's why
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post #15 of 16 Old 01-06-2013, 08:21 PM
Mean Max
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Checked for this problem?

http://www.hughesengines.com/Index/p...p?partid=27091

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No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

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