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Unread 11-03-2012, 11:46 AM   #1
Cjd99
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1994 YJ Wrangler 
 
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10 MPG? help!!!!

So I figured it out and I'm getting 10th mpg. Understandable if I was lifted and had bigger tires. But I'm all stock on 31s, no extra weight besides the winch. And I have a 4 banger. I know I shouldn't be getting that bad of gas millage. Any ideas on what may be wrong????

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Unread 11-03-2012, 02:24 PM   #2
pete1991YJ
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Hi there! Yeah thats pretty bad, mine is getting 20 MPG. First thing to do is a decent tune up.

Then make sure all your vacuum lines are tight - either put new ones or use hose clamps. Pay special attention to the small lines going into the intake, and also where it hooks nto the fuel pressure regulator. I did both.

Also check around the manifolds for leaks - they tend to work loose over time. This will kill the MPG's. Especially the bolts near the back of the engine, these work out and cause leaks.This throws off the O2 sensor and makes it run rich.

Make sure you have a 195 thermostat in there to keep the computer happy - it won't listen to the O2 sensor if its too cold, this will also kill the MPG's.

Hope that helps!
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Unread 11-03-2012, 03:05 PM   #3
UltimatE
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I agree, when was your last tune up?

Also would be a good idea to pull your engine codes and see if anything comes up.
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Unread 11-03-2012, 03:25 PM   #4
pete1991YJ
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Quote:
Originally Posted by UltimatE View Post
I agree, when was your last tune up?

Also would be a good idea to pull your engine codes and see if anything comes up.
Hey UltimatE, are you any good with electrics? I'm helping out this guy but I gotta go for several hours, its a cranking/starting issue - http://www.jeepforum.com/forum/f12/n...p-lot-1434157/
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Unread 11-03-2012, 04:18 PM   #5
UltimatE
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Also, for a reference, my 4 banger with 35's gets a surprising 15mpg.
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Unread 11-03-2012, 07:34 PM   #6
aaron580
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WOW! maybe time for a tuneup and maintenance? mine gets about 12 or so city with 35s and 4.56 gears and 7" lift....
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Unread 11-04-2012, 07:00 AM   #7
WakeDoctor
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I get 15 average. Best was 16.5 on the highway with 35's and 4.56. You just need to do some checking and tuning:

New plugs and cap, proper tire pressure (I would try max pressure before doing the line test), air filter (no need for aftermarket, keep it stock and clean), check the vac system as mentioned, new fluids won't hurt but make sure you put 10w30 in the motor and and trans if you are running a manuel, not a heavy weight oil. Seafoam is great stuff and it is possible that your intake needs a cleaning. Dump it in the tank first, if you still aren't satisfied try the booster line and then change your fuel filter after this. There is no telling what crap will break loose in your tank from this stuff. Another thing on the seafoam, do it before you change any plugs or O2 sensors. Some say it can fowl them out.
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Unread 11-05-2012, 08:16 AM   #8
Que89YJ
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Tune up. Check your codes:

http://www.jeepforum.com/forum/f12/h...codes-1257145/

Chances are a bad O2 or engine temp sensor near the tstat.
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Unread 11-05-2012, 11:53 AM   #9
Srisher
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mine gets 10mpg as well with 33's
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Unread 11-05-2012, 12:36 PM   #10
WakeDoctor
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Quote:
Originally Posted by Srisher View Post
mine gets 10mpg as well with 33's
He is running 31's with everything stock. Your Jeep is turning more weight and height with 33x12.50's. He should be getting way better than you.
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Unread 11-05-2012, 06:31 PM   #11
Cjd99
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Sorry for taking long ro reply. ok I will start checking things out tomorrow. My tires are at 33 OSI and I put new plugs in in the begining of the summer. Thanks for the ideas of what to check! U guys always help a lot. Also, would a leak in the back system cause it to run rough? Somedays it runs fine, and others it just runs rough and stalls when I push in the clutch for stops or corners
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Unread 11-05-2012, 07:10 PM   #12
TrentYJ
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Quote:
Originally Posted by UltimatE View Post
Also, for a reference, my 4 banger with 35's gets a surprising 15mpg.
Same boat here and I can confirm this. It may even push 16-17 on the highway with a tailwind
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