very bad gas mileage
#1
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Year: 2001
Model: Cherokee
Engine: 4.0
very bad gas mileage
Two days ago my jeep just decided it wanted to get bad gas mileage. Im getting about 150 miles to a tank. No codes thrown, i have no idea whats going on.
#3
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Year: 1994
Model: Cherokee
Engine: 4.0
Mine did the same thing and i had just completed a tuneup. Went back and changed the fuel filt and 02 sensor and mine went back to normal. PO had never changed the ff over 150000. Id also do as BowtieGuy3 says. A friend of mine had to change his MAP to get his mileage back up. Good Luck!!
#6
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Year: 1996
Model: Grand Cherokee
Engine: 4.0
I had a 97 rav 4 a few years back and had one of the vacuum lines cracked running to the mass air flow. It would not run for the like of the foreign booger. Maybe it was just that tank of gas you put in. Some gas can give you poor mileage depending on the condition of it.
#7
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Year: 1996
Model: Cherokee
Engine: 4.0L HO
Did you swap a big block into it Seems like it could be a sensor, like an O2 sensor going south or it already left. It can also be a coolant temp switch, if those are bad your computer will be in "limp home-open loop" mode so your fuel mileage would be horrible. Your MAP sends the signal to control the fuel delivery and ignition timing. Heres how you can check to see if its bad. You need a high impedance voltmeter and thats it.
Step 1: with key ON and engine off, the voltmeter reading should be approximately 5 volts even.
Step 2: IF not at 5 then its bad. haha...simple huh, but if not continue.
Step 3: Test MAP sensor terminal 1 and 2
Step 4: Start the Jeep and make sure the voltage is between 0.5-1.8 with engine idling.
Step 5: Then check at WOT or wide open throttle, and make sure the volts are reading between 3.9-4.8
Step 6: If the sensor doesn't on either of these then check the vacuum line for leaks or blockage. If it doesn't have one of these its most likely your sensor.
Step 1: with key ON and engine off, the voltmeter reading should be approximately 5 volts even.
Step 2: IF not at 5 then its bad. haha...simple huh, but if not continue.
Step 3: Test MAP sensor terminal 1 and 2
Step 4: Start the Jeep and make sure the voltage is between 0.5-1.8 with engine idling.
Step 5: Then check at WOT or wide open throttle, and make sure the volts are reading between 3.9-4.8
Step 6: If the sensor doesn't on either of these then check the vacuum line for leaks or blockage. If it doesn't have one of these its most likely your sensor.
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#8
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Year: 2001
Model: Cherokee
Engine: 4.0
Mine did the same thing and i had just completed a tuneup. Went back and changed the fuel filt and 02 sensor and mine went back to normal. PO had never changed the ff over 150000. Id also do as BowtieGuy3 says. A friend of mine had to change his MAP to get his mileage back up. Good Luck!!
#9
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Year: 1998
Model: Cherokee
Engine: 4.0
#10
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Model: Cherokee
I changed my O2 sensor, and my mpg went from 16 to 20. These things wear out. ) 01 model would have an O2 after the cat as well. I'd change them both at the same time if you can afford it. If not, change the one closest to the manifold first.
#11
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Year: 1987
Model: Cherokee
Engine: 4.0 liter RENIX I-6, DIY Cold Air Intake, 2.5 FM Exhaust, 3 Core Radiator
Yeah, that "fuel filter in the tank thing" came with the, I believe the 97+ XJs. The fuel filters in these are said to last until the fuel pump takes a dump. So, you change out both when opening up the gas tank. Trust, me. You won't want to do this just for the fuel filter. It is a royal PITA.
#12
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Year: 1998
Model: Cherokee
Engine: 4.0
Yeah, that "fuel filter in the tank thing" came with the, I believe the 97+ XJs. The fuel filters in these are said to last until the fuel pump takes a dump. So, you change out both when opening up the gas tank. Trust, me. You won't want to do this just for the fuel filter. It is a royal PITA.
#15
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Year: 1987
Model: Cherokee
Engine: 4.0 liter RENIX I-6, DIY Cold Air Intake, 2.5 FM Exhaust, 3 Core Radiator
X2 on lay off the D*** skinney pedal!!! Seriously, if you have no fuel leaks, then you have a bad MAP sensor or O2 sensor.