06 mileage drop after spark plug changes, no codes, no leaks, help???
I have an 06 4.0 sport ranger that has had a drop in gas mileage & power after some tuning up. No codes are thrown.
Tuneup was replacing spark plugs & seafoaming (1/3 in gas, 1/3 in oil, 1/3 in brake booster hose).
MPG calculated every single tank by starting with a 0 mileage trip meter, filling up & diving the trip mileage by gallons of gas. The very next tank after the tuneup resulted in a 3 MPG drop, every tank thereafter continued with the 3 MPG drop.
- No codes
- Smoke test showed no leaks
Things done to try and fix problem:
- Spark plug changes (tried different motorcraft plugs, then autolite plugs, then just had the dealership do the change)
- Changed oil & filter (a few times)
- Changed fuel filter
- Cleaned MAF
- Cleaned IAC
- Cleaned throttle body
- Cleaned EGR
- Replaced front O2 sensors
I'm running out of ideas. Help?