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-   -   Only 14.3 miles per gallon on new 4.2 L engine. (http://www.wranglerforum.com/f218/only-14-3-miles-per-gallon-on-new-4-2-l-engine-243304.html)

drwhitefox 05-17-2013 02:06 PM

Only 14.3 miles per gallon on new 4.2 L engine.
 
I put a new 4.2 L engine In my 1988 Jeep Sahara. And I'm only getting 14.3 miles per gallon whether I drive at 80 miles an hour or 65 miles an hour.
My old engine was getting 17 – 18 miles to gallon But it was fixing to crater.
Is there some sort of a harmonizer that you can hook up to the engine to find out If the engine or the carburetor or something is running rich .
If so what is the name of the machine I need to hook it up to.
I'm located in San Antonio Texas. Does anybody know of any shops that would handle that.

Nubby55 05-17-2013 06:24 PM

Did You use the same Carb.? adjust it with vacuum gauge and set the timing and wait for it to break in.

TreeClimber1 05-17-2013 06:30 PM

How much fuel have you ran thru the new engine?

drwhitefox 05-17-2013 11:26 PM

Quote:

Originally Posted by Nubby55 (Post 3766717)
Did You use the same Carb.? adjust it with vacuum gauge and set the timing and wait for it to break in.

No it's brand-new carburetor.

drwhitefox 05-17-2013 11:27 PM

Quote:

Originally Posted by TreeClimber1 (Post 3766734)
How much fuel have you ran thru the new engine?

About 35 gallons

drwhitefox 05-17-2013 11:28 PM

Quote:

Originally Posted by Nubby55 (Post 3766717)
Did You use the same Carb.? adjust it with vacuum gauge and set the timing and wait for it to break in.

Hey thanks for answering

drwhitefox 05-17-2013 11:30 PM

Quote:

Originally Posted by TreeClimber1 (Post 3766734)
How much fuel have you ran thru the new engine?

Thanks for answering

Odie4AZ 05-18-2013 07:59 PM

Where did you find your new engine? I've been looking but can only find a rebuilt from Automotix..

rkidd 05-18-2013 08:04 PM

:eek:I have a 84 cj7 with a 4.2l. Great motor but the carb. was junk from the factory. Switched to fuel injection. Problem solved.

Steampunk 05-18-2013 08:10 PM

Hey!

That engine needs to be broken in!!!!....tolerances may still be a little tight.....run it on dyno oil for a while and you will see the MPG and power slightly climb....

Later!

TreeClimber1 05-20-2013 10:52 AM

Quote:

Originally Posted by TreeClimber1 (Post 3766734)
How much fuel have you ran thru the new engine?

Quote:

Originally Posted by drwhitefox (Post 3767491)
About 35 gallons

Quote:

Originally Posted by Steampunk (Post 3769594)
Hey!

That engine needs to be broken in!!!!....tolerances may still be a little tight.....run it on dyno oil for a while and you will see the MPG and power slightly climb....

Later!

I was thinking the same thing. It's not uncommon for the fuel effeciency of an engine to get slightly better, with each tankful of fuel. But since he's gone thru at about three tanks, I'm thinking it's not going to get much better due to tolerances being tight.

ChicoJeepy 05-20-2013 12:22 PM

Heck I think my 93 Wrangler is getting about 20-25 MPG and I'm only using 3/4 of the 20 gallon tank.

Sworsen94wrangler 05-20-2013 12:30 PM

Wow I'm only getting 18 miles per gallon on my 94 yj

sevenservices 05-20-2013 12:48 PM

not engine related, but double check your tire pressure and also make sure none of the brakes are dragging. A low tire, or dragging brakes will totally kill your mpg. Even 5 pounds low can hit the mpg quite a lot.

ChicoJeepy 05-20-2013 12:53 PM

My tires are brand new from the early 2000's because when the state of Oregon stopped using steel studded tires and went to aluminum studs. So my set of Radial Wildcats are really nice thick walled tires and balanced. Good thing I kepted them all these years.

Jrgarcia715 05-20-2013 02:20 PM

You guys are all lucky I get about 10mpg on a good day


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