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.

Diagnostic Info:
- 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?

 

Bump.

 

Wirelessly posted

What did u clean the MAF & IAC with?

 

I see replaced front 02 sensor. That makes me think you got an aftermarket one?