Alright so I have a 2001 Jeep Cherokee. Completely stock. I'm getting terrible gas mileage. I'm hearing people getting like 14 or 15 mpg and I'm over here getting around 10. Maybe less. I fill up every week and I'm getting close to 200 miles a tank. Where should I start looking first? What sensors? Vacuum lines? Anything that might lead me to getting a little better gas mileage. Thanks guys.

 

last tune up?

driver habits (hard acceleration "jack rabbit starts")

5 garage sales worth of stuff in the back?

inproper/uneven tire inflation or poor alignment...

dragging brakes...

other half quit Weight Watchers...

That's your usual starting points for poor economy.

 

Try a tuneup.

 

How is the engine performing other than poor gas mileage?

Are you seeing stumble/hesitation at intial cold drive away?

Is the transmission torque converter going into lockup when cruising?

When was the last time you changed your spark plugs? What plugs are you using?

When was the last time the Oxygen Sensors were changed?

 

Seems to be performing well. I've only had it a year and it seems to still have decent power. On cold starts in the morning. The RPM's seem to go up higher then normal and it doesn't seem like it has the same power. I always thought that was because the engine was cold. I changed the plugs about 4 months ago to NGK Copper plugs. I had champion platinums in it but it was missing so I put the right plugs in. I have not yet changed any oxygen sensors and I thought about that and I did price them out. What sensors would have to be changed to improve gas mileage and how do I check to see if they are bad or not

 

I saw you have a 00'. here is an issue ive been having with my 01'. Its probably not linked to the bad gas mileage, but mine ran WAY better with insulation on the fuel line.

https://www.cherokeeforum.com/f2/02-...h-idle-180996/

 

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Normally the upstream Oxygen Sensors govern fuel economy but the downstream sensors play a big part in this roll. You shouldn't just replace the upstream sensors, especially if all the sensors are the same age. Retaining old downstream sensors with new upstream sensors may trigger a CEL (per 2001 diagnostics manual).

Oxygen Sensors are only good for 100,000 to 120,000 miles, depending on contaminants running through your engine (Seafoam, et al)

As far as checking the Oxygen Sensors; it's a long drawn out process that may lead you nowhere, ending up changing them anyway.

If you could access a scanner that shows live data with the engine running it would show you what the Oxygen Sensors are doing.

Other than that...

Having a 2001 XJ, I take it this the exhaust setup you have (PIC). Note the NTK Oxygen Sensors are listed in a chart on the pic. I wouldn't recommend Bosch sensors for your XJ. NTK sensors are available through Rockauto.com.