the check engine light came on -97 Explorer 4.0 I just did new Ford spark plugs/wires. air filter looks clean. gas filter looks like it's been there for many miles. had Auto Zone do computer check, came up with one code P1151. could be low fuel pressure, suggest changing fuel filter which I did. I disconnected battery to reset computer. I'm taking a 2 hour trip tomorrow with car, will see if check engine light comes back on. question- would a dirty fuel filter give you poor gas mileage? with about 80% city driving, I'm getting about 11 mpg's. is this low? what else would trigger a P1151 code that would kill my gas mileage. the engine runs perfect though with a nice smooth idle and no hesitation at all.

 

Have you checked your O2 sensors? A bad one could throw this code and account for the poor fuel economy. You could also try cleaning the MAF, though I think that one is a long shot if you aren't having any driveability issues.

 

I just took a 220 mile roadtrip. all highway with some hills. avg.70 mph with A/C on entire trip. I got 19 mpg. check engine light never came on. not too bad with the gas mileage. the O2 sensors look original. I might go ahead and change the left/right front ones. even though no check engine light, I might be able to squeeze a little more miles per gallons out. I also raised the tire pressure from 27 psi to 32 psi all around.