High pressure fuel pump replaced and electrical wires replaced, then 2 months later..

[joliett]

My Jeep 2021, 21k miles recently had the high pressure fuel pump replaced after having intense engine loss of power past 2000 rpm. After replacement and it's control wires repaired, the engine performed brilliantly for about 2 months.

Then on a 600 mile Interstate trip I noticed - like a switch turned on - my mileage reading dropped to 18 mpg. Previously my mileage never dropped lower than 20. I reset the mpg gauge, but again 18mpg appeared.

I'm concerned about what I should do next. I thought I should bring the jeep back to the dealer to diagnose the problem. It could be as simple as a bad spark plug. I think jeep will charge me for the diagnosis or should this all be under warranty.

The dealer that did this work on the High Pressure fuel pump is not trusted by me anymore, as he refused to diagnose my failed steering box, and actually told me to bring the Jeep elsewhere (I thought the service manager and I were on great terms.) But my new service dealer replaced the steering box with no problems, and now my steering is GREAT.

I am guessing it could be a bad spark plug, cat converter, or something minor. And I would think this diagnosis should be covered under warranty, but I'm not certain. If I have to, I guess I have to pay for diagnosis.

Any help here, my forum friends?

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[JEEP4U]

This 600 mile trip...........I'm sure it had elevation/temperature changes, which will affect mileage.

 

[joliett]

Thank you for your reply. That trip had nohing to do with the drop in mileage. As a matter of fact it was along the Atlantic coast up and down I-95.

My post was questioning what technically I could do to figure out why my mileage dropped 10% after driving 20k miles and through 2 seasons.

 

[four low]

No codes if you put a Code Reader on the OBD2 port ?
A drop in mpg with no corresponding issues could be as simple as headwind, fuel quality, tire pressures.
If the Sky is Falling, something usually hits you in the head first.

 

[joliett]

Since refilling with summer gas the last few months, my mpg returned to 21-22 mpg. The ethanol used in winter blends really did make a difference. Ethanol blend 18 mpg - Summer gas 21 - 22 mpg. My Rubicon returns to perfect ...

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