Only 14.3 miles per gallon on new 4.2 L engine. - Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > YJ Jeep Wrangler Forum > YJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 05-17-2013, 02:06 PM   #1
Newb
 
Join Date: Oct 2011
Posts: 8
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.

drwhitefox is offline   Quote
Old 05-17-2013, 06:24 PM   #2
Jeeper
 
Join Date: Aug 2011
Location: north of St.Franisville La.
Posts: 2,639
Send a message via Yahoo to Nubby55
Did You use the same Carb.? adjust it with vacuum gauge and set the timing and wait for it to break in.

Nubby55 is offline   Quote
Old 05-17-2013, 06:30 PM   #3
Jeeper
 
TreeClimber1's Avatar
 
Join Date: Nov 2011
Location: Washington
Posts: 390
How much fuel have you ran thru the new engine?
__________________
1992 YJ, 401 V8, EFI, TH400, Atlas, D60s, Detroits, Warn 8274, Cage, 37 Krawlers
1997 TJ, 350 V8, EFI, TH400, Atlas 4spd, D60s, Detroits, Warn 12000, Cage, 40 Kevlars
TTC 1994, TTC 2012, Trail Tour participant.
TreeClimber1 is offline   Quote
Old 05-17-2013, 11:26 PM   #4
Newb
 
Join Date: Oct 2011
Posts: 8
Quote:
Originally Posted by Nubby55 View Post
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 is offline   Quote
Old 05-17-2013, 11:27 PM   #5
Newb
 
Join Date: Oct 2011
Posts: 8
Quote:
Originally Posted by TreeClimber1 View Post
How much fuel have you ran thru the new engine?
About 35 gallons
drwhitefox is offline   Quote
Old 05-17-2013, 11:28 PM   #6
Newb
 
Join Date: Oct 2011
Posts: 8
Quote:
Originally Posted by Nubby55 View Post
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 is offline   Quote
Old 05-17-2013, 11:30 PM   #7
Newb
 
Join Date: Oct 2011
Posts: 8
Quote:
Originally Posted by TreeClimber1 View Post
How much fuel have you ran thru the new engine?
Thanks for answering
drwhitefox is offline   Quote
Old 05-18-2013, 07:59 PM   #8
Jeeper
 
Odie4AZ's Avatar
 
Join Date: Dec 2011
Location: Prescott, AZ
Posts: 74
Where did you find your new engine? I've been looking but can only find a rebuilt from Automotix..
Odie4AZ is offline   Quote
Old 05-18-2013, 08:04 PM   #9
Jeeper
 
rkidd's Avatar
 
Join Date: Aug 2011
Location: Maryland
Posts: 93
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.
rkidd is offline   Quote
Old 05-18-2013, 08:10 PM   #10
Jeeper
 
Join Date: Jan 2013
Posts: 154
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!
__________________
2009 JK X 2 door
Stock for now.
Steampunk is offline   Quote
Old 05-20-2013, 10:52 AM   #11
Jeeper
 
TreeClimber1's Avatar
 
Join Date: Nov 2011
Location: Washington
Posts: 390
Quote:
Originally Posted by TreeClimber1 View Post
How much fuel have you ran thru the new engine?
Quote:
Originally Posted by drwhitefox View Post
About 35 gallons
Quote:
Originally Posted by Steampunk View Post
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.
__________________
1992 YJ, 401 V8, EFI, TH400, Atlas, D60s, Detroits, Warn 8274, Cage, 37 Krawlers
1997 TJ, 350 V8, EFI, TH400, Atlas 4spd, D60s, Detroits, Warn 12000, Cage, 40 Kevlars
TTC 1994, TTC 2012, Trail Tour participant.
TreeClimber1 is offline   Quote
Old 05-20-2013, 12:22 PM   #12
Mr Jeepy of California

WF Supporting Member
 
ChicoJeepy's Avatar
 
Join Date: May 2013
Location: Chico, CA.
Posts: 466
Heck I think my 93 Wrangler is getting about 20-25 MPG and I'm only using 3/4 of the 20 gallon tank.
__________________
My back yard. Sutter Buttes. Best 4 wheeling around! All private owned and few get to enjoy it's rugged beauty first hand.
1993 Jeep Wrangler YJ 2.5L AX5 Transmission Rough Country 4" Suspension Lift 27" Wildcat Tires and Stock Wheels KC Fog Lights OEM Push Guard White SmittyBilt Soft Top with Rugged Ridge Hardware CB Radio Full Sound System.....
ChicoJeepy is offline   Quote
Old 05-20-2013, 12:30 PM   #13
Newb
 
Join Date: May 2013
Posts: 2
Wow I'm only getting 18 miles per gallon on my 94 yj
Sworsen94wrangler is offline   Quote
Old 05-20-2013, 12:48 PM   #14
Founder, ThumbJeeps

WF Supporting Member
 
sevenservices's Avatar
 
Join Date: Sep 2009
Location: Mid-Michigan/Thumb
Posts: 3,952
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.
__________________
-Chris
Founder, ThumbJeeps


1994 Wrangler YJ I6 4.0 H/O Auto 3 spd. 4" RC (33x12.5) (15x8) 3:54 Gears
sevenservices is offline   Quote
Old 05-20-2013, 12:53 PM   #15
Mr Jeepy of California

WF Supporting Member
 
ChicoJeepy's Avatar
 
Join Date: May 2013
Location: Chico, CA.
Posts: 466
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.
__________________
My back yard. Sutter Buttes. Best 4 wheeling around! All private owned and few get to enjoy it's rugged beauty first hand.
1993 Jeep Wrangler YJ 2.5L AX5 Transmission Rough Country 4" Suspension Lift 27" Wildcat Tires and Stock Wheels KC Fog Lights OEM Push Guard White SmittyBilt Soft Top with Rugged Ridge Hardware CB Radio Full Sound System.....
ChicoJeepy is offline   Quote
Old 05-20-2013, 02:20 PM   #16
Jeeper
 
Jrgarcia715's Avatar
 
Join Date: Mar 2013
Posts: 141
You guys are all lucky I get about 10mpg on a good day

Jrgarcia715 is offline   Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Download our Mobile App

» Featured Product

All times are GMT -5. The time now is 03:39 AM.


User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.

Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC