Was getting 10MPG on '03 Ford Van E350 5.4L automatic with 260k miles.
No leaks or burns, and usually 15MPG+.
Changed MassAirFlow sensor and MPG popped to 16.3, but mileage dropped back to 12 after 1 tank of fuel.
No engine fail lights at any time. Also changed the AirFilter at time of MAS change.
DPFE? MAF fail on new unit?
Has new CatConv and coil packs, plugs have maybe 10k. No EngFail Lt is confusing. Any ideas?
Why'd you suspect MAF sensor failure was the initial problem? Get a scan tool that reads live data and look at the MAF sensor data. Sitting still and idling the MAF sensor should read 5.4 grams of air per second. Did you use an OEM Motorcraft sensor or a knockoff when you replaced it?
Look at your short and long term fuel trims as well.
