99 Explorer 4x4 mileage drop off

I've lost mileage performance suddenly and i dont know why. Before the drop off i was gettin 17-18 around town and 20+ Freeway. I dont have a lead foot and i havent changed driving habits. Had it hooked up to the computer at the dealership and my PIDS are all normal. I've changed my sparkplugs(didnt change wires, those are still fairly new) and my fuel filter. I've done the fuel injection cleaner additives and stuff, but still crap mileage, gettin now 13-15 around town and 18-19 freeway. If u have any ideas they would be much appreciated. thanks in advance.

Don't know how it affects mileage, but cleaning or replacing the air flow sensor helps my Fords. Get electrical component cleaner (Radio Shack $11) and clean the wires inside the sensor. You'll need to remove the twin anti-tamper screws (special screwdriver bit at Sears-$2), and take it out carefully. Just squirt the filaments and put it back together. Helps a lot with pinging, and I think also helps mileage.

maybe you have a bad Oxygen Sensor....They will directly affect mileage as they degrade. Get the codes checked maybe you might get a O2 code. But they dont alwasy give codes as they are on there way out. You can aslo try some Sea Foam into your intake. I have read alot about that..It cleans carbon buildup out of your intake and cylinders...

I would also reset my computer after cleaning the Mass airflow sensor, so it can relearn the new airflow. Do this by diconnecting battery negative for about 10 minutes.

cool, ill give that a shot, every little bit helps i guess. I work at a car dealership and the mechanics i work with were tellin me that during the winter, gas companies put additives in the fuel to make it more oxygen rich. They think thats the problem. Thanks for ur advice and ill do that this weekend.

Yep that is true...I read a lot in the forums that the "winter mix" kills the gas mileage.

Good luck..
V