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2001 Jeep HORRIBLE GAS MILEAGE!!!!

1

1989JeepCherokee

NAXJA Forum User
Location
Omaha NE
I have a 2001 XJ that gets about 150 miles to a full tank (my 89 that I had stolen around 300). I just got it about 2 weeks ago so I do not know how long its been since things have been changed. Except for the ignition coil pack that I changed about a week ago.
Anyone now what the problem could be?

No mods at all w/58,000 miles.
My 72 year old grandma tells me I drive slow so I don't think I'm the problem.
 
Last edited:
Welcome to NAXJA!

There is a wealth of info available here that is only a quick *search* away. Try using that to see if an answer already exists. Chances are it does and you can save yourself a lot of time.

Meanwhile, are you getting a CEL? You may wish to you a code scanner and see if there are any stored codes. Typically, bad O2 sensors can jack up mileage.
 
O2 sensors, MAP or either temp sensor! If none of the above you are pissing fuel as you drive............:D
 
1989JeepCherokee said:
Not since I replaced the coil pack.
Click to expand...

jpmagazine.com search for "mileage master" there is a three part article on XJ milage, should give you some ideas.

I vote basic tuneup first--NGK V plugs, cap and rotor (brass contacts), spark plug wires, air filter.

I would DEFINITELY flush the cooling system and replace the thermostat on a 9 year old granny wagon--its been sitting quite a bit.
 
Does the temp come up to what it should? X2 on thermostat and upstream O2 sensor(s), each of those has brought me from 17-18mpg down to 12-13.
 
Don't rely on getting a CEL with a lazy o2 sensor.

Your 195 degree thermostat should get you up to approximately 205~210 degrees on the gauge. BTW, I only install and recommend Stant SuperStat Premium thermostats, 195 for the 4.0 XJ.
 
NAPA has a sale on their filters and tune up parts.
 
My 88 does that too...145-150 miles per tank during the week...but it has 348k on the ticker, and my drive to wrok is 2 miles.

Now, let me get out on the highway, and it is back up to 300 or so per tank

My guess would be a bad temp sensor, as it seems to think it isn't warmed up yet
 
TRCM said:
My 88 does that too...145-150 miles per tank during the week...but it has 348k on the ticker, and my drive to wrok is 2 miles.

Now, let me get out on the highway, and it is back up to 300 or so per tank

My guess would be a bad temp sensor, as it seems to think it isn't warmed up yet
Click to expand...

You won't hit normal operating temperature until about 20 minutes of operation have occurred.

Normal operating temperature is not when the thermostat opens and the gauge gets to the 205~210 range of the gauge. The whole engine must be fully warmed up, and that takes a lot longer.
 
For suspected gas mileage issue, it's best to calculate your actual mileage (miles driven divided by gallons consumed) rather than to extrapolate as to how many miles to a tank of gas you're getting.

Write it down every time, get at least 3 samples, more is better. Mileage can vary tank to tank, driver to driver, weather fluctuations, etc.

Doing this gives you a better shot of knowing exactly where you're at.
 
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