Sep 21, 2015, 03:49 PM
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XJ Ask the Question Thread
No, I don't lick fish.
Joined: Mar 2011
Posts: 11,169
Likes: 26
From: Northern Kentucky
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
Ok so I'm driving myself crazy cuz I can't figure this out. I have a 96 jeep grand cherokee with 160k miles it's a 4.0l straight 6. I bought this jeep it ran great until i left the dome lights on and the battery went completely dead a new battery was put in it before I bought it so I jumped it and then it would not idle at all. The vehicle sat for 6 months before I bought it so I figured maybe the gas was bad. I was a 1 owner and the lady is 80 years old so I figured she didn't drive it much. I put 93 octane in it along with a fuel injection cleaner in it and it started to stay running but the idle was very low. I cleaned the throttle body with a cleaner and eventually replaced the IAC (idle air control) valve cuz the original one was pretty gummed up and while I had the part out I used a spray gun cleaning brush with a foaming upper engine and fuel injector cleaner to manually scrub all parts I could. I followed the instructions on the upper engine cleaner I bought from the GM dealership I work at. Condensed version is spray into throttle body while running until can is empty then let sit with vehicle off for a half hour then start and run at 2500 rpms until all the blue and black smoke billowing out of the tailpipe is gone. After replacing the part, cleaning and disconnecting the battery terminals for a minute or so I started it up again. It ran perfect. idle was perfect, throttle response was perfect. After about 100 miles or so I'm right back to it stalling and not idling. During that 100 miles it very slowly got worse and worse every time I started it. Any suggestions on what is goin on or what I'm failing to see?
Newbie
Joined: Dec 2016
Posts: 9
Likes: 0
From: Arizona
Year: 2000
Model: Cherokee
Engine: 4.6L I6
That is vaguely normal, it depends on exactly how accurate the engine's coolant temperature sensor is (can verify with IR gun on the thermostat housing, or check it versus the IAT with the engine cold).
For OEM type thermostats, 195°F is the temperature that it starts to open at. As it heats it opens more. Most 4.0L XJs tend to hover in the 210°F range, and the system doesn't consider itself really warm until about 218°F which is when the electric fan turns on.
With the AW4 you've got a heat exchanger with the engine cooling system. So the transmission's heat is discharged via the normal rad, but if it's a LOT (such as low-speed, towing, and mountainous terrain...) heat from the transmission can wind up being ADDED to the engine.
There are a few simple things you can do, first I would verify that the ECT is reporting properly (likely is, or is only off by a couple degrees). Second is make sure the radiator isn't clogged, both by using a pressure washer or garden hose to push bugs and the like back out the front (you'd be amazed at how much crap builds up between the fins) and by doing a full coolant flush, if you haven't already. The old style glycol and anti-corrosion additives these things were shipped with was only good for about 3 years, and a lot of XJs were neglected so quite a few have sludge.
You can also give this a spin: https://www.cherokeeforum.com/f2/free-quick-fix-41821/ Doesn't cost anything, good maintenance.
The other things include a replacement of the fan clutch, which is a viscous coupling that starts to let go as they age, and adding in an auxiliary transmission cooler. In your climate and terrain this is DEFINITELY a good idea. You can plumb it inline, before the ATF hits the radiator, or set it up so the ATF only goes through the standalone rad. In your area I wouldn't be concerned about the transmission being too cold!
For OEM type thermostats, 195°F is the temperature that it starts to open at. As it heats it opens more. Most 4.0L XJs tend to hover in the 210°F range, and the system doesn't consider itself really warm until about 218°F which is when the electric fan turns on.
With the AW4 you've got a heat exchanger with the engine cooling system. So the transmission's heat is discharged via the normal rad, but if it's a LOT (such as low-speed, towing, and mountainous terrain...) heat from the transmission can wind up being ADDED to the engine.
There are a few simple things you can do, first I would verify that the ECT is reporting properly (likely is, or is only off by a couple degrees). Second is make sure the radiator isn't clogged, both by using a pressure washer or garden hose to push bugs and the like back out the front (you'd be amazed at how much crap builds up between the fins) and by doing a full coolant flush, if you haven't already. The old style glycol and anti-corrosion additives these things were shipped with was only good for about 3 years, and a lot of XJs were neglected so quite a few have sludge.
You can also give this a spin: https://www.cherokeeforum.com/f2/free-quick-fix-41821/ Doesn't cost anything, good maintenance.
The other things include a replacement of the fan clutch, which is a viscous coupling that starts to let go as they age, and adding in an auxiliary transmission cooler. In your climate and terrain this is DEFINITELY a good idea. You can plumb it inline, before the ATF hits the radiator, or set it up so the ATF only goes through the standalone rad. In your area I wouldn't be concerned about the transmission being too cold!
Good to know about the heat exchanger... I was under the impression that this was an aux oil cooler, but maybe I should consider adding one. I do think I'm due for a pressure washing of the radiator, I'll try that.
Temperature reporting from the sensor seems to be correct - the readings make sense, and are in line with what I was seeing with my cheapie thermal cam.
I did adjust my throttle kickdown a little while back, but great idea there - I think that's an easy one to miss.
I'll keep an eye on the viscous fan clutch... this afternoon I'm going to pop my belt off and see if I can feel any play in my water pump. From the videos I've watched, seems like that would be an indicator that it was worn. Also using this opportunity to tension my belt correctly... checked it yesterday, and it was in the ~50lb range, when I hear it should be 180-200.
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
I do think I'm due for a pressure washing of the radiator, I'll try that.
Temperature reporting from the sensor seems to be correct - the readings make sense, and are in line with what I was seeing with my cheapie thermal cam.
I did adjust my throttle kickdown a little while back, but great idea there - I think that's an easy one to miss.
I'll keep an eye on the viscous fan clutch... this afternoon I'm going to pop my belt off and see if I can feel any play in my water pump. From the videos I've watched, seems like that would be an indicator that it was worn.
Temperature reporting from the sensor seems to be correct - the readings make sense, and are in line with what I was seeing with my cheapie thermal cam.
I did adjust my throttle kickdown a little while back, but great idea there - I think that's an easy one to miss.
I'll keep an eye on the viscous fan clutch... this afternoon I'm going to pop my belt off and see if I can feel any play in my water pump. From the videos I've watched, seems like that would be an indicator that it was worn.
Don't spend too much time on that. If it's not slipping you're good. But if you need to replace the belt anyway, get a Continental Elite (previously known as Goodyear Gatorback). They need much less tension to do the same job, easier on you and the bearings.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
1994 XJ engine.
I need to hook up an oil pressure tester to verify the new oil pump is working. I assume I can just use the factory sending unit's port, but I want to ensure I buy a tester that includes the correct adapter.
Can anyone tell me what that port is? I'm guessing 1/8" NPT
I need to hook up an oil pressure tester to verify the new oil pump is working. I assume I can just use the factory sending unit's port, but I want to ensure I buy a tester that includes the correct adapter.
Can anyone tell me what that port is? I'm guessing 1/8" NPT
CF Veteran
Joined: Aug 2015
Posts: 1,226
Likes: 11
From: Laurium, MI
Year: 1999
Model: Cherokee(XJ)
Engine: 4.0L
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
CF Veteran
Joined: Jan 2013
Posts: 19,219
Likes: 45
From: west chester, pa
Year: 1999
Engine: 4.0
Originally Posted by salad
This thread and the other one have been renamed, you get one Internet Cookie.
Apparently you didn't know that we have an MJ section :P
Apparently you didn't know that we have an MJ section :P
CF Veteran
Joined: Aug 2015
Posts: 1,226
Likes: 11
From: Laurium, MI
Year: 1999
Model: Cherokee(XJ)
Engine: 4.0L
Newbie
Joined: Mar 2017
Posts: 3
Likes: 0
Year: 2000
Model: Cherokee
Engine: 4.0L
2000 Jeep Cherokee 4.0L
Today i hit the gas and ran it all the way to redline. Right after, check engine light started to blink and when i stopped it ran rough. Shut off and turned back on and it idled fine and the light was solid. Codes came back for cylinder 1,2, and 6 misfires, multiple cylinder misfires and small evap leak. Also the oil pressure is really low. Normally, idles at 30 and drives at 60. Now it idles at about 20 and drives around 40. I have no clue whats wrong. Pulled the plugs and they should be replaced but no build up or oil on any. Checked the coolant and its still perfectly green. No odd smells of gas , coolant or oil in the exhaust either. I need some help. I cant find this combination of problems anywhere.
Last edited by Hunter Cundiff; Mar 26, 2017 at 09:30 PM.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Member
Joined: Feb 2009
Posts: 101
Likes: 1
From: Tampa, FL
Year: 96
Model: Cherokee
Engine: 4.0
CV fix lowers mileage
Here's a stumper: For the three months I have had my current 96 XJ 4.0, the CV system of elbows and vacuum hoses was all broken and disconnected. I finally got around to installing new elbows and hoses. (I know I did it right, with the wide-open elbow in front and the restricted one in back.) There was no effect on engine behavior/performance (I wasn't expecting any, it's always run pretty smooth), but since I got the CV system going, there has been a sudden and marked drop in gas mileage. My only guess is that the changed has forced the computer to recalibrate stuff, but I dunno. Any ideas? I wasn't getting any tailpipe smoke or other ill effects before.... I'm halfway tempted to disconnect it again.
