I have a 98 4.0 OHV. And it seems to be getting about 10 mpg. I recently changed the plugs and wires, air filter, and it gets regular oil changes. I also changed the fuel filter, which was pretty restricted, and it seemed to make the fuel consumption worse, even w/o the a/c on.

 

Any Codes? There are so many possibilities, did this happen all at once, or gradually? Need more info.

 

I too have a '98 w/ the 4.0 SOHC...I've tried everything and it's just a gas pig. The fact that it only has a 17 gal. tank makes it seem like you're fueling up more often also.
The best thing I found for mileage is to go extremely light on the accelerator pedal. Other than the mileage, it's an extremely reliable little SUV. :-)

Scott

 

Maybe a previous owner installed a performance air filter that uses oil (such as a K&N) and that oil coated the Mass Air Flow (MAF) sensor. In the early stages this can cause a decrease in fuel economy without impacting driveability. I had this happen on a 1993 Taurus SHO, the fuel economy took a nose dive but the performance was just fine. After checking the plugs and wires I removed the MAF sensor from the housing, noticed it was very dark, cleaned the elements with some electrical parts cleaner (this was before they had specific MAF sensor cleaner) and almost immediately my fuel economy was back where it should be.

Depending on how many miles are on the Explorer you may want to consider replacing the oxygen sensors as well. If they have over 60k miles on them, changing them out will probably make an improvement in economy as well.

And finally, you might want to try using SeaFoam or a similar product to decarb your engine. I'd suggest the "through a vacuum port" method rather than just adding it to the fuel tank.

-Rod

 

Never thought of that... I put a K&N on my '98 Sport and shortly after the check engine light came on and stayed on. I think I'm gonna clean the sensor and put a stock filter back on it. Thanks for the tip !

Scott