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Unread 05-20-2012, 01:59 PM   #1
Pragmaticdoc
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1988 YJ Wrangler 
 
Join Date: May 2012
Location: Columbus, Indiana
Posts: 51
Gas mpg situation.

i own an 87yj 258 2bbl 5speed. it geta ten miles to the gallon. doesnt matter if i baby it or drive like a teenager. i used to own a 79 CJ7 258 clifford intake holley 4bbl 4 speed. if i kept my foot out of it got almost 18 miles per gallon. What gives? It has had a complete tune up and always run mid-grade fuel. Is it as simple as i bought the cj off a certified mechanic and the yj from a redneck?

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Unread 05-27-2012, 08:58 PM   #2
SquidsYJ
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1993 YJ Wrangler 
 
Join Date: Jul 2011
Location: Norfolk, Virginia
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Doc: It could be any number of possibilities. Fill out your profile so folks have a better idea about the mods your jeep has and let us know what you have done to try and trouble shoot your problem.

Does your speedometer indicate speed correctly? Do you have a fuel leak? Is your carb adjusted properly? Do you have a vacuum leak?

I would also suggest trying in the YJ tech section.
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Unread 05-28-2012, 12:02 PM   #3
Pragmaticdoc
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1988 YJ Wrangler 
 
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Location: Columbus, Indiana
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I cant fill out my profile yet not enough posts. 87 YJ 258 5speed weber 2 barrel 2 inch body lift. 33x12.5 super swampers. Engine rebuilt 25000 miles ago. Broke in properly. Carb was rebuilt for a second time by Weber. Still runs like she has a V8 under the hood but still only gets 10 mpg. Gears tranny etc all stock.

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Unread 05-29-2012, 08:16 AM   #4
SquidsYJ
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1993 YJ Wrangler 
 
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Location: Norfolk, Virginia
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You've got a nice looking jeep!

Does your speedometer indicate your correct speed? This seems kind of simple, but if your speedometer is off so will your mileage for your MPG calculations. Usually the faster you go the more your speed will be off.

Have you tried to adjust your weber? It could just be set too rich or the choke might need to be adjusted.

I know in a jeep, especially topless and doorless, you would have smelled it, but have you physically checked for a fuel leak?

Another thought. When the engine was rebuilt, was it de-stroked, did it get a more aggressive cam, or anything like that?

I still think you should consider posting this up over in the YJ section, there more of the yj guys will see it and someone might have a better solution. You could try posting just a link to this thread. I'm not strong with carbs, so I could be missing something obvious to a carb guy.

Last edited by SquidsYJ; 05-29-2012 at 08:18 AM.. Reason: After thought
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Unread 05-29-2012, 01:41 PM   #5
Pragmaticdoc
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1988 YJ Wrangler 
 
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Location: Columbus, Indiana
Posts: 51
Yes the speedometer is off but have figured that into the algebra, Its not running rich or to thin. The Weber guy fiddled with it for quite a while. It was rebuilt to complete stock specs. Brand new block. not a refurbished one. Stock cam...other than the Weber and accel coil which is not any better than the stock one. Stock ignition other than that. I will try to figure out how to do the whole post another topic with a link to this one.
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Unread 05-29-2012, 05:20 PM   #6
SquidsYJ
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Location: Norfolk, Virginia
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This link is a thread in the YJ section. The third post has a couple links that might help.
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Unread 05-30-2012, 08:28 AM   #7
Pragmaticdoc
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Location: Columbus, Indiana
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Thanks for the link. Thanks for the help.
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Unread 05-30-2012, 12:33 PM   #8
RookieJeeper01
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1987 YJ Wrangler 
 
Join Date: Apr 2010
Location: Everett Wa
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In my 87 YJ with 4:56 gears, AX15 5 speed, 34s and 258 nuttered with a weber I always got 10 no matter what. A while back I threw on a 4.0 head and MPI and now I always get 13 with alot more power and easier start ups. I also have removed the 2 piece axle and hubs up front. Replaced with TJ axles that are always spinning which is supposed to cost me a little gas mileage.

I think I could get 14 out of it, but have not had any decent road trips and drive in traffic alot when I daily drive it to work.
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