The short story is a while back my MPG dropped signiicantly, >20%, at say 65mph. I found the LTFT was almost +20 as I cruised along. I think I found a CEL won't get set till it hits 25. magically adding sea foam to gas tank really helped LTFT and mpg. LTFT dropped to +5. But the LTFT would creep back up after several tanks. I found I could pull the fuel line at the pump, under the hood, empty line and give put a capful of sea foam in line and it has same positive effect on LTFT. I suspect the Fuel pressure sensor is what is being affected by sea foam. I think its supposed to be 2% accurate. I really should just replace it but little nervous pulling intake manifold, although I would love to see how much oil on back of valves. but so easy to just add sea foam.
I Changed Air Filter, O2 sensor.
So my question is, for anyone that is getting good highway mpg, what is your LTFT when cruising, also at idle, mine runs +10 to +15 at idle, what yours.
My STFT seems to mover around, plus and minus.
A positive fuel trim number means the engine is getting more gas than optimum, so a weak fuel pump can't be cause, it would have to be putting out too much pressure, I suspect the fuel pressure senor is out of tolerance.
How hard is intake manifold to remove ? I have not see any youtube videos specific to this 2.0 engine.
by the way, I took it to dealer before warranty was over, with +20 LTFT and they just blew me off , said nothing was wrong with car.
thanks