Gas milage drops with outside air temp


2000 F150, 4.6L Triton, 165000 miles The truck rus good, I have no trouble codes. Fuel pump just replaced due intermitent operation. The mileage porblem has been apperant since I have had the truck at 135000 miles, 1 1/2 years ago. Mileage averages about 18.5 to 19 during the summer, and drops to 17.5 or less in the winter. The colder the weather, the less mileage. When the wather warms 20 degrees or more, the mileage spikes, but then drops back to whatever average is for that temp. Driving conditions are always the same, as I work at an office and use the same route each day. My suspician is a bad Mass Air Flow Sensor, but I would like to know how to verify this before spending the bucks to replace it. I had a similar situation with a 1993 Ranger. I would attribute it to local fule mixing, except for my 1996 escort that never varies in mileage. Any suggestions?

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Friday, January 12th, 2007 AT 4:54 PM

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A dirty or slightly patinated filament will send the wrong air reading to the computer, saying it is getting more air than it really is and the computer will tell the EFI to send in the wrong mix of fuel, thus, the bogging. The patina seems to form faster if you live in a damp climate. If you have had bogging or missing or idle spots, about every 25K miles plan on this quick cleaning job:
When your engine is cool, remove the wiring clip from the side of the black plastic sensor part of the MAF aluminum body. To remove the MAF interior sensor wire, you will need a Security Star (Size T15 or T20) screwdriver or screwdriver bit for a power screwdriver. Remove the two security star-head screws and carefully remove the sensor. You will see the two sensor filaments they look almost like the filaments on a light bulb. Carefully spray the filaments with an O2 safe carburetor cleaner, such as Gumout. Let it dry thoroughly. I help mine along with a careful blast or two of canned dry air. While it is drying carefully wipe the aluminum mount surface of the MAF body if there is any dust there, but be careful not to get dust in the mount hole. When the sensor is dry, replace the sensor back in the MAF body and secure with the security star-head screws. These don't need to be torqued down, just simply hand tight. Replace the wiring clip. Then start up your engine.

Do you use snow tires in the winter, have longer warm ups? Ate O2 sensors giving good wave patterns?

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Friday, January 12th, 2007 AT 5:02 PM

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