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Unread 06-03-2012, 10:38 AM   #31
NonRubicon
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1990 YJ Wrangler 
 
Join Date: Nov 2009
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sd92110-

While you don't get a Jeep for it's fabulous fuel economy, you should at least squeeze as much as you can out of it by making sure it's running as well as it can. When I was having problems with my carter my economy was low (~13mpg). The same for my Howell TBI setup - I just recently solved the EGR intake leak (needed to tighten the EGR tube nut)and with the last tank I got ~15 mpg, whereas before it was around 12-13mpg. Still ran decently though with that intake leak. While 12mpg seems to be common for YJ's, it might not be for your case.

Unless you are hauling some extra weight, tools, gear, accessories, a properly running carter should get you around 15mpg in the city, assuming no major hills to climb. I don't know what witchcraft plym49 has done to his carter, the best I ever saw with the stock Carter was 18 mpg on the freeway (31" tires, 3.55 gears). A rack would create some drag though. Might as well do some checking to make sure that 12-13 is the best you can get out of your YJ.

I'm assuming you still have the OEM setup with the Carter -
-Start by looking for any vacuum or intake leaks. The computer will compensate for the extra O2 and dump more fuel to balance out the mix.
-Make sure the stepper motor is working properly since this is what affects the fuel delivery. It should be centered and constantly moving forward/back once the computer takes over.
-Make sure the carb isn't dripping fuel - either from the bowl or venturis.
-I'd also do a full tune up if it has been a while - plugs, wires, rotor, cap (Team Rush if not already done), fuel filter, oil change, timing. O2 sensor also.

An all electric engine in a YJ - the brick-like aerodynamics of a Wrangler probably wouldn't result in good mileage, also considering the weight of all the batteries. If you notice production electrics and hybrids, they are almost as much about aerodynamics as they are efficient engines. Put the 4.2L in a more aerodynamic shell and you'll likely get better than 20+mpg city/highway (seeing as plym49 already gets nearly that in his YJ)

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Unread 06-03-2012, 10:45 AM   #32
WindsorRenegade
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Maybe the addition of a small electric motor that you can switch on at your own convinience would be kinda neat. Think of all the torque!


AH! My YJ was just giving me the most evilest of looks when I spoke of putting an electric motor in it.
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[QUOTE=ruthole;13615845]I just bumped it around till it was in the hole and she went right in. But my hands were hard to fit in there. [/QUOTE]
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Unread 06-05-2012, 11:53 AM   #33
Tanrer
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Quote:
Originally Posted by Tanrer View Post
I get that wit my 33s but i have various power/economy upgrades so id say that's about right, hell i get 8mpg offroad/hauling
and i forgot to say i don't drive in 2wd ever(vacuum harness was missing when i bought it so its manually engaged with a bungee heh, heh)
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Unread 06-05-2012, 01:25 PM   #34
rodgers3
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Quote:
Originally Posted by Tanrer

and i forgot to say i don't drive in 2wd ever(vacuum harness was missing when i bought it so its manually engaged with a bungee heh, heh)
Well there's your problem
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Unread 06-05-2012, 01:56 PM   #35
Anticanman
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What did you manually engage with a bungee?
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Unread 06-06-2012, 02:51 AM   #36
WindsorRenegade
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Quote:
Originally Posted by Anticanman View Post
What did you manually engage with a bungee?
....yeah. What the hell? lol Listen, if there's stuff I can do with bugnee cords, I'm all ears.
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[QUOTE=ruthole;13615845]I just bumped it around till it was in the hole and she went right in. But my hands were hard to fit in there. [/QUOTE]
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Unread 03-02-2013, 08:44 PM   #37
Tanrer
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the axle disconnect
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Unread 03-02-2013, 09:11 PM   #38
Reno72
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MyJeep is my economy car, my other rides are a 2500HD with 6.0 and a 1500AWD Express Van. I leave a huge carbon footprint just to piss Pelosi and Gore off.
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Unread 03-03-2013, 07:14 AM   #39
giggityjeeper
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Quote:
Originally Posted by sd92110 View Post
Just calculated my gas mileage at 11-12 miles per gallon, OUCH!
4.2l 6 cylinder 5 speed manual transmission.
Gov. site says it should be 15 city 20 hwy.
I have a rack on it but whoa..
172 miles on a a full 15 gallon tank of fuel...
Anyone wanna buy a Jeep??

Any Ideas??
Quote:
Originally Posted by sd92110 View Post
send the jeep to them, have them ship it back once they fix it......

that what I tell ppl when they come in and say, 'well the kelly blue book says online my car is worth this'.....cool send it to them and have them send you a check.....

I love these fuel milage threads
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Unread 03-03-2013, 06:13 PM   #40
deathtrap
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Quote:
Originally Posted by Reno72 View Post
MyJeep is my economy car, my other rides are a 2500HD with 6.0 and a 1500AWD Express Van. I leave a huge carbon footprint just to piss Pelosi and Gore off.
Ha, mine gets around 15-16, and sad to say it probably the most fuel efficient of the 4 vehicles I own. stick it to the man!
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Unread 08-24-2013, 03:53 PM   #41
RICEKILA
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Mostly around town -- no highway driving -- 95 - 4cyl - 5spd. - 4.11 - 31" tires - the last tank -- 17.36 gals. / 302 miles = 17.38 MPG
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Unread 08-24-2013, 09:45 PM   #42
iflypa28
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Quote:
I'm assuming you still have the OEM setup with the Carter -
-Start by looking for any vacuum or intake leaks. The computer will compensate for the extra O2 and dump more fuel to balance out the mix.
-Make sure the stepper motor is working properly since this is what affects the fuel delivery. It should be centered and constantly moving forward/back once the computer takes over.
-Make sure the carb isn't dripping fuel - either from the bowl or venturis.
-I'd also do a full tune up if it has been a while - plugs, wires, rotor, cap (Team Rush if not already done), fuel filter, oil change, timing. O2 sensor also.
This is a good place to start and I would add a couple things to the list. I have an 88 4.2 as well and was getting 12mpg. I found two problems that brought it right up to 16.5mpg (mixed hwy/city) unfortunately I don't know which one fixed it but it was probably both anyway.

My choke was not disengaging all of the way so I put a manual one in, although I could have just fixed it, this was definitely making it run a little rich.
Secondly I had a vacuum leak that was causing the flapper door in the air intake to not open which was probably acting like a choke stuck full on and causing it to run rich. This door should open immediately when the engine starts.
After I fixed these the jeep ran MUCH better to as you can imagine!
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