12.36 MPG Help - 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 > 12.36 MPG Help

August special - FREE XJ Unibody stiffeners when you buy a~Artec JK 1 TON SWAP~Dan's Old as Dirt Birthday Sale!

Reply
Unread 02-01-2013, 07:37 AM   #1
calpbs
Registered User
1994 YJ Wrangler 
 
Join Date: Jul 2009
Location: Ringgold, Georgia
Posts: 84
12.36 MPG Help

So I have read some threads and here is where I am. 1994 4.0 177000 miles, K&N, New thermostat, electric fan, new water pump. Seems to have a decent tune up. Runs well. 33's with 4.10's I installed a 35 tooth speedo gear.. I checked with both a gps and calculated RPM in gear and it is dead on. Based on the dash gauge I cant get the engine temp above 150 or 160 when driving. So am I in open loop mode getting crappy mileage. I anticipate a complete tune up to include cleaning the throttle body and replacing the O2 sensor. It does not show any codes, I hate throwing money at a problem. Any advise or suggestions would be appreciated.

008-9-.jpg  
__________________
I have done so much with so little for so long, I can do anything with nothing forever.

Charlie Lamar
Ringgold, GA
calpbs is offline   Reply With Quote
Unread 02-01-2013, 08:02 AM   #2
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,595
Dash guage is garbage. Check to see if the fan clutch is stuck. Take out the thermostat and put it in a pot of water and heat it and see what temp it opens. The thermostat sounds like the problem but the guage on the cluster should be checked against the radiator. Keep in mind there is about a 10 degree difference but not 30. You could look inside the radiator and use the thermometer and check to see what the temp is when you coolant starts to flow. Also you can verify the temp on both your guage and the front sensor with a meter by checking the resistance. It is possible that the guage sensor or the engine temp sensor are wrong/bad. I just threw everything at you. Don't get overwellmed by the info. It is an easy one to figure out. Don't do the O2 sensor until you know the cooling system is functioning right. It would just be a waste of money.
yjgaugespecs-1-.jpg   coolant-temp-sensor-scale.jpg   328825_image0.png   coolantandairtempchart.jpg  
Que89YJ is online now   Reply With Quote
Unread 02-01-2013, 03:59 PM   #3
calpbs
Registered User
1994 YJ Wrangler 
 
Join Date: Jul 2009
Location: Ringgold, Georgia
Posts: 84
I replaced the thermostat, I replaced the sensor in the thermostat housing. I have an adjustable thermostat electric fan. I checked the temp with my laser tester and it was tracking close. I dont know what else needs to be done to keep the temp up during driving. The ambient temp is around 45 F. The cooling system appears to be working. I dont get it
__________________
I have done so much with so little for so long, I can do anything with nothing forever.

Charlie Lamar
Ringgold, GA
calpbs is offline   Reply With Quote
Unread 02-01-2013, 04:05 PM   #4
Xpress
Registered User
1989 YJ Wrangler 
 
Join Date: Dec 2010
Location: The Great Big Box, California
Posts: 5,806
I'd imagine 45* might have a play on your system. Is the thermostat the correct temperature?
__________________
[url=http://www.jeepforum.com/forum/f12/another-5-2l-yj-thread-1503048/][FONT="Arial Black"][COLOR="Lime"][SIZE="4"]My 5.2L Build thread[/SIZE][/COLOR][/FONT][/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 02-01-2013, 09:50 PM   #5
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,595
I gave you the list. Thermostat is opening too early. Needs to be at 185. Or the fan is coming on too early.
Que89YJ is online now   Reply With Quote
Unread 02-02-2013, 01:04 AM   #6
ROTTEN
Registered User
1994 YJ Wrangler 
 
Join Date: May 2011
Location: SGF, NY
Posts: 755
You have my symptoms. And my solution is the thermostat for fact. My temp is your temp and my mileage sucks.
__________________
I'm new
ROTTEN is offline   Reply With Quote
Unread 02-02-2013, 11:16 AM   #7
calpbs
Registered User
1994 YJ Wrangler 
 
Join Date: Jul 2009
Location: Ringgold, Georgia
Posts: 84
I replaced the thermostat. It is a 195 fail safe unit from auto zone. I adjusted the fan to come on at roughly 190 but when driving it cools down and doesn't get warm, so far. I am not sure what to do next
__________________
I have done so much with so little for so long, I can do anything with nothing forever.

Charlie Lamar
Ringgold, GA
calpbs is offline   Reply With Quote
Unread 02-02-2013, 11:21 AM   #8
calpbs
Registered User
1994 YJ Wrangler 
 
Join Date: Jul 2009
Location: Ringgold, Georgia
Posts: 84
How do you know where you are with respect to the ECU if no check engine light is on?
__________________
I have done so much with so little for so long, I can do anything with nothing forever.

Charlie Lamar
Ringgold, GA
calpbs is offline   Reply With Quote
Unread 02-11-2013, 07:11 PM   #9
calpbs
Registered User
1994 YJ Wrangler 
 
Join Date: Jul 2009
Location: Ringgold, Georgia
Posts: 84
I was told the fail safe units do not hold temp well. I have now replaced back to a new stant 195 unit. on a 94 wrangler there are 2 temp sensors. One on the back of the head reports to the gauge, the other in the water neck reports to the ECU. I dont know why the temp wont stay up. I dont know what to do
__________________
I have done so much with so little for so long, I can do anything with nothing forever.

Charlie Lamar
Ringgold, GA
calpbs is offline   Reply With Quote
Unread 02-12-2013, 09:55 AM   #10
ratmonkey
R.I.P.
 
ratmonkey's Avatar
1997 ZJ 
 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,805
Fail safe thermostats suck.
Get a stant or oem.
__________________
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

ratmonkey is offline   Reply With Quote
Unread 02-12-2013, 10:19 AM   #11
pete1991YJ
Registered User
1991 YJ Wrangler 
 
Join Date: Mar 2012
Location: Niagara Falls, NY
Posts: 1,625
Use Stant or Robertshaw for cooling system stuff.
__________________
***--- Wrecking Crew member ---***
"I've prolly been around longer than you think"
pete1991YJ is offline   Reply With Quote
Unread 02-12-2013, 10:56 AM   #12
JCashen
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2013
Location: Fort Worth, Texas
Posts: 222
Sorry to hi-jack your thread.

I am wondering if cooler temps means worse gas mileage for wranglers. Reason I ask is that is the same temp my gauge reads while driving and my gas mileage sucks at 10-11.4mpg
JCashen is offline   Reply With Quote
Unread 02-12-2013, 11:14 AM   #13
ratmonkey
R.I.P.
 
ratmonkey's Avatar
1997 ZJ 
 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,805
Quote:
Originally Posted by JCashen View Post
Sorry to hi-jack your thread.

I am wondering if cooler temps means worse gas mileage for wranglers. Reason I ask is that is the same temp my gauge reads while driving and my gas mileage sucks at 10-11.4mpg
Yes, as he has a wrangler that would be the conclusion you may draw from this and several hundred other threads like it.
It might not be your only problem, but it is a big one.
__________________
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

ratmonkey is offline   Reply With Quote
Unread 02-12-2013, 11:41 AM   #14
rodgers3
Registered User
1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: imperial, missouri
Posts: 1,044
I noticed a drop due to winter mix gas. And the cooler temp.
In the summer i was getting flatline 20. right now i get anywhere between 14-18
rodgers3 is offline   Reply With Quote
Unread 02-12-2013, 11:51 AM   #15
pete1991YJ
Registered User
1991 YJ Wrangler 
 
Join Date: Mar 2012
Location: Niagara Falls, NY
Posts: 1,625
It will go down some due to the cooler outside temps and winter gas mix. But not *that* much. Example, my 4-banger went from 20 MPG's down to ~18 MPG's. Getting less than 15 is usually a sign of something wrong bigtime. In this cast the cooling system thermostat. FWIW I just replaced my radiator and T-stat with the best that NAPA had last summer, and it holds rock steady at 200F. Total cost was about $180.
__________________
***--- 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.