Terrible MPG from my Jeep lately.

[Chris142]

Granted Jeeps are not know for good MPG but this is excessivly bad. I always check my MPG when I get gas.

It's always gotten 18 on the hwy and 15.5 around town which is normal.

Last few tanks it has been less than 15.5 in town. I noticed 13mpg a couple weeks ago. Last tank was 11.5 mpg.

No codes. Runs fine. Plugs only have 3k on then, air filter clean, tires not low.

Replaced the upper O2 sensors 10k ago.

I don't see anything unusual on my scan tool. IAT and coolant temps ok, timing ok, O2 sensor voltages are moving.

Ideas?

 

[urrlord]

Maybe a Seafoam/hot water flush followed by some hi-rpm driving.

 

[tig1]

Change in fuel formula for the summer. Happens here also to produce less emissions and less money in our pocket.

 

[Chris142]

Originally Posted By: tig1
Change in fuel formula for the summer. Happens here also to produce less emissions and less money in our pocket.
In the past it's gotten better mpg with summer fuel.

 

[5sfe91]

Maybe the injectors are getting a little dirty, run some seafoam or other injector treatment in the tank

 

[FZ1]

Try a different gas station.

 

[Chris142]

Originally Posted By: FZ1
Try a different gas station.
Done that. We only have 3 suppliers here.

AM/PM has their own trucks and everybody else buys from the local Shell or Chevron dealer. My currant tank is Chevron as is most stations here.

Have not been buying from the Shell supplied stations lately due to price.

 

[Astro14]

Bad coolant temp sensor causing it to run in "open-loop" would cause that...may not throw a code...just cause the ECM to think the engine is cold...

 

[HTSS_TR]

Chevron Techron fuel system cleaner if you didn't use any for more than a year. I agree with Astro14, bad temperature sensor may be the culprit, I had similar problem with LS400 a couple years ago, changed temperature sensor brought back the MPG lost.

 

[synthetic_crazy]

Heavier foot lately? Using the A/C more?

 

[jeepman3071]

Engine? Year? Model?

 

[The_Eric]

You didn't mention if you've replaced the fuel filter lately?

 

[jorton]

Originally Posted By: Astro14
Bad coolant temp sensor causing it to run in "open-loop" would cause that...may not throw a code...just cause the ECM to think the engine is cold...


Check the oil fill hole when the engine is cold. Can you smell fuel?

 

[Chris142]

Originally Posted By: Astro14
Bad coolant temp sensor causing it to run in "open-loop" would cause that...may not throw a code...just cause the ECM to think the engine is cold...
According to my scanner it's reading actual engine temp of 195-205.

 

[Chris142]

Originally Posted By: HTSS_TR
Chevron Techron fuel system cleaner if you didn't use any for more than a year.
Gets that about once a month.

 

[Chris142]

Originally Posted By: synthetic_crazy
Heavier foot lately? Using the A/C more?
Not any more than normal and the AC wont kill the mpg that much.

 

[Chris142]

Originally Posted By: jeepman3071
Engine? Year? Model?
02 wrangler 4.0L

 

[Chris142]

Originally Posted By: The_Eric
You didn't mention if you've replaced the fuel filter lately?
It's part of the fuel module. Replaced with a new one from the dealer 15k ago.

 

[eljefino]

Fan clutch seized? You'd notice, I'm sure. Hot brake?

 

[Chris142]

Originally Posted By: eljefino
Fan clutch seized? You'd notice, I'm sure. Hot brake?
Fan clutch is very aggressive but it's been on there several years.
Good call on the brakes. I have not smelled anything from them but I will check them tomorrow when I get to work.