Same old problem - 4 banger and highway speed - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > Same old problem - 4 banger and highway speed

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineRubicon Express Suspensions from CCOR 706-207-4140Smittybilt Hard Tops @ Oconee Off-Road! 706-534-9955

Reply
Unread 04-10-2013, 06:02 AM   #1
jcarr74015
Registered User
1987 YJ Wrangler 
 
Join Date: Feb 2011
Location: catoosa, ok
Posts: 95
Same old problem - 4 banger and highway speed

Ok after a nightmare intruing to get the girl running right again I now have the age old highway speed issue to deal with.

4.10 gears factory, 33x12.50 TSL boggers, and a PO botched 3" body lift. Springs are probably shot the have no arch in them the are well not frowning but are flat.

When finally getting her on the highway last night I could get about 55 mph out of her then started getting a vibration. No matter how hard I pushed the old girl 57-58 was it no more. It was like I was out of power. This is my first 4 banger pushing 33s, is this normal? I can deal with the low speed as long as I know I don't have another problem.

By the way the speeds I posted are GPS speeds, speedo shows 7-10 mph less.


I've read lots of threads about highway speed in relation to the gears and tires but don't recall any also naming the 4 banger in the mix.

Thanks for your informative replies in advance.

jcarr74015 is offline   Reply With Quote
Unread 04-10-2013, 06:26 AM   #2
Old4X
Registered User
1990 CJ7 
 
Join Date: Nov 2008
Location: Ga
Posts: 4,963
What gear were you in and what RPMs?
__________________
418 miles on 19 gallons of gas. Can't beat the BBD !
Old4X is offline   Reply With Quote
Unread 04-10-2013, 06:51 AM   #3
Louie4
Powah Injanir
 
Louie4's Avatar
1993 YJ Wrangler 
 
Join Date: Aug 2008
Location: Raleigh, NC
Posts: 9,886
Sounds about normal especially if you were going uphill. You'll need to put some deeper gears in to get that acceleration back (4.56 or 4.88) with the larger tires. Of course it's never a bad idea to give the 2.5L a tune-up. Though it won't be that much better, it couldn't hurt. As for the speedo you'll need a different speedometer gear with more teeth to accommodate the tire size. The required tooth count will change if you put different gears in though.
__________________
Lou

I have a jeep...and it is modified...I win.

YJOTM July 2012
YJOTM February 2014

Louie4's YJ Build
Poison Spyder Fender Install
Warn M8000 Rebuild Adventure
University of Georgia
Louie4 is offline   Reply With Quote
Unread 04-10-2013, 07:20 AM   #4
MLJeeper
Registered User
1988 YJ Wrangler 
 
Join Date: Nov 2004
Location: Birmingham, Al.
Posts: 5,029
No thats not normal. I am able to cruise 65 to 70 except for steep hills when it would drop down to around 55. I run 35s and 4.56s now. Still get the same speeds. Cruising right at 65 gets me the best fuel mileage.
__________________
Your limited slip differential sucks.

Quote:
Originally Posted by Anticanman View Post
Any video of the sound?
MLJeeper is offline   Reply With Quote
Unread 04-10-2013, 08:49 AM   #5
bogleparsons
Registered User
2013 JK Wrangler 
 
Join Date: May 2011
Location: fayetteville, NC
Posts: 1,875
If you were trying to use fifth gear then yes that's normal.

Try just staying in forth gear and you can get a bit more power. just a teeny bit anyway haha
__________________
If it's not supposed to move and does use duct tape.
If it's supposed to move and doesn't use WD40
bogleparsons is offline   Reply With Quote
Unread 04-10-2013, 09:16 AM   #6
Xpress
Registered User
1989 YJ Wrangler 
 
Join Date: Dec 2010
Location: The Great Big Box, California
Posts: 5,807
The 2.5L isn't a high powered engine, it's an economical engine. You've basically gone up 5 tire sizes over factory tire size, so what did you expect? The 6 cylinder even has issues pushing big tires on stock gears. Re-gear to 4.88 or drop down to 29" tires is about your only option if you want to maintain highway speeds.
__________________
[URL="http://www.jeepforum.com/forum/f12/another-5-2l-yj-thread-1503048/"]My 5.2L Build thread[/URL]

-1989 Jeep Wrangler 2.5L, soon to be 5.2L
-1996 Jeep Grand Cherokar 5.2L, donor and rainy day driver
-2004 Kawasaki KLR650 sunny day driver
[QUOTE=mudsweatNgearz;21162729]Leave em off and weld an I beam on. Bumperetts just scream homo.[/QUOTE]
"A well regulated Militia, being necessary to the security of a free State, the [B][I]RIGHT[/I][/B] of the people to keep and bear Arms, [B][I]SHALL NOT BE INFRINGED[/I][/B]."
Xpress is offline   Reply With Quote
Unread 04-10-2013, 11:05 AM   #7
GrantYJ
Registered User
1992 YJ Wrangler 
 
Join Date: Mar 2009
Location: Neosho, Missouri
Posts: 844
I agree with MLJeeper and BogleParsons...
I have a '92 4 banger with a ton of miles factory gears (4.10) and 33" MTs. On the flats I can run 70 all day no problem in 4th gear. If you throttle body injection ('91 or older) I don't know how well they do, but if yours is'92 or newer, you have a problem somewhere.
__________________
“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values
GrantYJ is offline   Reply With Quote
Unread 04-10-2013, 07:21 PM   #8
jcarr74015
Registered User
1987 YJ Wrangler 
 
Join Date: Feb 2011
Location: catoosa, ok
Posts: 95
Ok guys its an 87 and t-body injection. The engine is fresh and it has a new fuel pump filter plugs distributor and pretty much all new.

Don't have a tach hooked up yet so no rpms to report but the 55 is in 4th gear. I know the timing could use some tweaking.
jcarr74015 is offline   Reply With Quote
Unread 04-10-2013, 07:41 PM   #9
pete1991YJ
Registered User
1991 YJ Wrangler 
 
Join Date: Mar 2012
Location: Niagara Falls, NY
Posts: 1,628
There is some setup and adjustment that has to be done to the t-body injection systems, that Que knows about, I'm not up on the details of those. By comparison, I'm able to do 65 on the flats all day with 31's and stock gearing on MPFI. Not much more than that, tho - a little rise or a headwind means downshifting.
__________________
***--- Wrecking Crew member ---***
"I've prolly been around longer than you think"
pete1991YJ is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.