2000 Cherokee 4.0L MPG Issue
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Joined: Feb 2018
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Model: Cherokee(SJ)
2000 Cherokee 4.0L MPG Issue
hey everyone! I'm new here but I've had my 2000 Cherokee 4.0L for about 2.5 years and recently I've been having a huge dilemma with my fuel mileage, and I'm hoping to get some help from the forum. I'll try to give as much detail as I can to try to see if y'all can figure out what my problem might be.
Recently (the last few months) I've been consistently getting about 12-13 mpg no matter how I drive it: city, highway, mixed, you name it. When I first got the Jeep it was running great and getting satisfactory mileage returns (about 15-16 around town and even 22 one time when I drove to Wildwood, NJ from my home in SEPA, but typically high teens on the highway). In an attempt to try to remedy this recent issue, I've replaced the following:
the coil pack (after the CEL showed a code for a misfire) (Delphi brand)
the fuel pump (Delphi again)
spark plugs (OEM spec Champions)
all 4 o2 sensors (NTK)
the MAP sensor (NAPA brand)
and the coolant temp. sensor (again, NAPA brand)
I also had the throttle plate cleaned and ran injector cleaner through it a few times, but alas I'm still getting horrible mileage and I'm at my wit's end. I keep track of all of my mileage and around this time last year I was getting 14-15 just driving around town. The Jeep seems to run and drive okay it just sucks gas for some unknown reason. The Jeep only has 75,000 miles on it, and I've put about 20,000 on it. The only modifications I've done is putting 30x9.50 tires on it (it had 235/75/15s on it when I bought it) but it's done okay MPG-wise with the 9.50s and I put a straight pipe on from the cat back, but I quickly put the original muffler and tailpipe back on due to the noise. The only real issue the Jeep has is that the lifters make a lot of noise every now and then but it isn't consistent. That's the only thing I could think of that could maybe be causing the problem, since it seems like everything else should be fine. Thanks again everyone!
Recently (the last few months) I've been consistently getting about 12-13 mpg no matter how I drive it: city, highway, mixed, you name it. When I first got the Jeep it was running great and getting satisfactory mileage returns (about 15-16 around town and even 22 one time when I drove to Wildwood, NJ from my home in SEPA, but typically high teens on the highway). In an attempt to try to remedy this recent issue, I've replaced the following:
the coil pack (after the CEL showed a code for a misfire) (Delphi brand)
the fuel pump (Delphi again)
spark plugs (OEM spec Champions)
all 4 o2 sensors (NTK)
the MAP sensor (NAPA brand)
and the coolant temp. sensor (again, NAPA brand)
I also had the throttle plate cleaned and ran injector cleaner through it a few times, but alas I'm still getting horrible mileage and I'm at my wit's end. I keep track of all of my mileage and around this time last year I was getting 14-15 just driving around town. The Jeep seems to run and drive okay it just sucks gas for some unknown reason. The Jeep only has 75,000 miles on it, and I've put about 20,000 on it. The only modifications I've done is putting 30x9.50 tires on it (it had 235/75/15s on it when I bought it) but it's done okay MPG-wise with the 9.50s and I put a straight pipe on from the cat back, but I quickly put the original muffler and tailpipe back on due to the noise. The only real issue the Jeep has is that the lifters make a lot of noise every now and then but it isn't consistent. That's the only thing I could think of that could maybe be causing the problem, since it seems like everything else should be fine. Thanks again everyone!
CF Veteran
Joined: Dec 2015
Posts: 2,139
Likes: 93
From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
I get about 18-19mpg during the summer with 30x9.5 tires as well.
It has been a very cold winter (Northeast). Has it been the same where you are? Do you let your vehicle warm up before leaving? I notice that significantly reduces the miles I get from the tank for actual driving. Also when the temps are as low as they have been this year I notice my fuel trims (I run real time data) are quite rich while the vehicle warms up, and run a bit more on the rich side than normal during normal driving. Also I do not get the same power from the winter formula gasoline, so that reduces my miles per tank as well. I bet I'm getting about 15mpg during the winter as well, but I am not currently tracking it to be sure.
Considering you are going from about 18mpg down to 14-15mpg, is it possible that it is just a combination of these mundane things?
It has been a very cold winter (Northeast). Has it been the same where you are? Do you let your vehicle warm up before leaving? I notice that significantly reduces the miles I get from the tank for actual driving. Also when the temps are as low as they have been this year I notice my fuel trims (I run real time data) are quite rich while the vehicle warms up, and run a bit more on the rich side than normal during normal driving. Also I do not get the same power from the winter formula gasoline, so that reduces my miles per tank as well. I bet I'm getting about 15mpg during the winter as well, but I am not currently tracking it to be sure.
Considering you are going from about 18mpg down to 14-15mpg, is it possible that it is just a combination of these mundane things?
CF Veteran
Joined: Nov 2017
Posts: 3,700
Likes: 238
From: Groton, MA
Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
I get about 18-19mpg during the summer with 30x9.5 tires as well.
It has been a very cold winter (Northeast). Has it been the same where you are? Do you let your vehicle warm up before leaving? I notice that significantly reduces the miles I get from the tank for actual driving. Also when the temps are as low as they have been this year I notice my fuel trims (I run real time data) are quite rich while the vehicle warms up, and run a bit more on the rich side than normal during normal driving. Also I do not get the same power from the winter formula gasoline, so that reduces my miles per tank as well. I bet I'm getting about 15mpg during the winter as well, but I am not currently tracking it to be sure.
Considering you are going from about 18mpg down to 14-15mpg, is it possible that it is just a combination of these mundane things?
It has been a very cold winter (Northeast). Has it been the same where you are? Do you let your vehicle warm up before leaving? I notice that significantly reduces the miles I get from the tank for actual driving. Also when the temps are as low as they have been this year I notice my fuel trims (I run real time data) are quite rich while the vehicle warms up, and run a bit more on the rich side than normal during normal driving. Also I do not get the same power from the winter formula gasoline, so that reduces my miles per tank as well. I bet I'm getting about 15mpg during the winter as well, but I am not currently tracking it to be sure.
Considering you are going from about 18mpg down to 14-15mpg, is it possible that it is just a combination of these mundane things?
I recently drove my Dad's ('16 or 17') Tacoma and it tracks the mpg per tank. I idled for a short time (much less than I idle my XJ or family car) and the mpg had dropped nearly a full 1 mile. This was a bit of a shock - not that the mpg went down, but just how dang fast it did on a bigger engine. I routinely idle for long periods of time in the family car (my wife is adamant about no jackets on the kids in their car seats), but with the 4cyl vvt engine with an avg mpg in the mid 30's, I don't notice a big difference.
On my XJ I've been getting -roughly- 14-15 mpg with mostly "city" driving and warming it up when it's been sitting for more than a couple hours, but I was getting closer to 20 last Oct/Nov before the daily arctic temps.
CF Veteran
Joined: Dec 2015
Posts: 2,139
Likes: 93
From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
If that were true, you would most likely see a problem like that expressing itself in the fuel trim values obtainable from an OBD2 scanner. The O2 sensors would see that too much oxygen was remaining in the exhaust and would be signaling the computer to increase the fuel trim (make it more rich). So instead of seeing fuel trims hovering around 0% you might see them constantly higher in the 5-10% range or even maxed out. Even if just one injector was failing, it would probably result in some unwanted fuel trimming. (or all vice versa if one or more injectors was constantly providing too much fuel, which would be more rare).
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CF Veteran
Joined: Apr 2014
Posts: 1,181
Likes: 60
From: Florida
Year: 1999
Model: Cherokee
Engine: 4.0l
If that were true, you would most likely see a problem like that expressing itself in the fuel trim values obtainable from an OBD2 scanner. The O2 sensors would see that too much oxygen was remaining in the exhaust and would be signaling the computer to increase the fuel trim (make it more rich). So instead of seeing fuel trims hovering around 0% you might see them constantly higher in the 5-10% range or even maxed out. Even if just one injector was failing, it would probably result in some unwanted fuel trimming. (or all vice versa if one or more injectors was constantly providing too much fuel, which would be more rare).
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