4.2 gasmilage - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-18-2002, 01:37 PM Thread Starter
 
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4.2 gasmilage

On average my 258 gets 10.5 mpg in the YJ. IT is nuttered and i do understand that there is more gas than needed goin into the engine. Would it be possible to put the meetering needles in some? Any ideas in inmproving as mileage untill next year when i get a new carb?
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post #2 of (permalink) Old 12-18-2002, 01:45 PM
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Re: 4.2 gasmilage

Gas Milage has so many factors. My Yj nuttered with 36's and 258 and 4.56 gears got around 10-11 also. If you want better gas milage you should get fuel injection!! Mike
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post #3 of (permalink) Old 12-18-2002, 01:49 PM
 
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Re: 4.2 gasmilage

</font><blockquote><font class="small">In reply to:</font><hr />
Any ideas in inmproving as mileage untill next year when i get a new carb?

[/ QUOTE ]

It would probably be a little better if the computer and it's sensors and stuff worked properly (It doesn't since you nuttered it), but I doubt there's a big difference.

Fuel injection is the way to go. I get about 16 around town with my TBI, and close to 20 on the interstate. That's with 3.54 gears, 33" tires, and a 4 speed Tranny. I imagine the highway millage would be a little higher if I had a 5 speed. Right now, 75 MPH is about 3000 RPM.
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post #4 of (permalink) Old 12-19-2002, 06:24 AM
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Re: 4.2 gasmilage

87. If it makes you feel any better... I have been faced with serious carb probs in my Waggie for the past month and change.. I was getting 6-7 MPG driving in traffic, and just 8 highway. I was going to the gas station about every two days... And I don't drive that much.
I just finished a total carb rebuild, and I expect that my #'s will come up a bit. But I still have to replace the plugs... I am sure they are pretty gummed up after running so poorly for two months.
You may have done this already, but you could just try a full tune up. Ne plugs, wires, rotor, and Cap. Total cost is about $40 But if you can save some MPG then that will pay for itself pretty quick. At least it does/is for me.
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post #5 of (permalink) Old 12-19-2002, 06:53 AM
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Re: 4.2 gasmilage

I'm currently doing 13 MPG with a 2.5L '93 YJ. And I hate it! [img]images/graemlins/mad.gif[/img] I was at some 20 MPG in the summer, but since the winter came around... I'm changing my sparks next week, and I'm also going to try to re-route the air intake back to get colder air. I'll let you know if it did any good...
post #6 of (permalink) Old 12-19-2002, 07:19 AM
 
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Re: 4.2 gasmilage

Choke operation and warm-up time play a big role in cold weather fuel economy. Personally, I wouldn't make any moves to get more cold air into the engine. It will make fuel economy worse by slowing down the warmup, increasing the fuel that remains as a liquid not a vapour. Cold air improves power if you get atomization, the charge is denser having the cylinder fill with more air and fuel, but it doesn't help with fuel economy. 100% vapourization of liquid fuel gives you the best fuel economy. Restore the heat stove, electric manifold heater, if any, coolant heated intake operation, if any, and adjust choke to come off as soon as the motor can run without it.
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post #7 of (permalink) Old 12-19-2002, 07:39 AM
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Re: 4.2 gasmilage

</font><blockquote><font class="small">In reply to:</font><hr />
adjust choke to come off as soon as the motor can run without it

[/ QUOTE ]
[img]images/graemlins/confused.gif[/img] [img]images/graemlins/confused.gif[/img] [img]images/graemlins/confused.gif[/img]
How do U do that? My YJ is injected, and as I recall, its fuel mixture is computer-controlled. I didn't know I could do such a thing as to change/adjust the choke.
I was told that (my) YJ's computer does one thing which could be good and bad at the same time... When the engine is cold, it gets a pre-definded, fixed mixture of air &amp; fuel, and it consumes more (while qwarming up). But unlike most of the cars I see around, it doesn't lower the fuel/air ratio gradually as engine warms up, but it rather keeps it up at maximum all the way until engine is at operating temp. And I was told that's why it gets so poor MPG in the winter.
Is that all BS, or does it really go that way? And how do you adjust the choke?
post #8 of (permalink) Old 12-19-2002, 07:51 AM
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Re: 4.2 gasmilage

I get around 10 mpg with mine, and it's MPI with a 4.0 head! [img]images/graemlins/frown.gif[/img] Of course I am running an automatic, 35" tires and 3.54 gears. I think once I get my gear ratio back down to the right size (4.56) It will help the mpg out. I'm just waiting for the funds to build axles to match the gears! [img]images/graemlins/grin.gif[/img]
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post #9 of (permalink) Old 12-19-2002, 09:07 AM
 
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Re: 4.2 gasmilage

BlueDevil, ok, that's a big Duhh [img]images/graemlins/blush.gif[/img] on my part with the "adjust the choke" suggestion. Definately [img]images/graemlins/crazy.gif[/img] didn't get enough sleep last night to have the thought process to realize that you have fuel injection. Sorry! Next thing I'll be telling you is to change your points!
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post #10 of (permalink) Old 12-19-2002, 11:51 AM
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Re: 4.2 gasmilage

I've checked my gas milege many times and I get between 12-15 with my 304 and t999 tranny. I'm turning about 2300 rpm @65mph. If I drive locked in 4wd it still gets about 10mpg.
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