pcm calibration:

[STANGM89]

i had my wifes expedition in at the ford dealership to replace 2 coils and they reprogramed the pcm to the latest calibration and since then the gas milage went from 19mpg to 14 mpg and they said the pcm wouldnt cause the milage to drop and said the fuel filter could be bad i thought a bad filter it would run rough .but it was getting great milage before i took it to them.any help would be greatly needed. thanks billy

 

[b1ackfang]

The PCM can cause your mileage to drop as it controls the engines fuel management. Granted the recalibration may or may not have caused this. I would take it back to them and have them diag it and see why the mpg went down.

I dont see a fuel filter causing that drastic of a drop though.