My 98 F150 with 4.6 has 44K miles on it and idles around1200 rpm. I get lousy gas milage, 12 mpg. around town. I just bought it last month and love it, it's my very first Ford truck. Is this too fast an idle? It has an auto transmillion and lots of power and runs smoothly.

 

I suppose it could be one of a million things, could be something as simple as a throttle body sensor adj to who knows what. Maybe you can get some codes off it at a local parts store for cheap and see if the computer is calling out anything. Idle should be around 6-700 if im not mistaken.

 

are there any mods? it is possible that the throttle cable needs adjustment. other than that the computer does all the work.

try a computer reset once done start the truck and let it idle for 5-8 min so the computer can re-learn the idle. if it goes back to the high idle there is definately something wrong!

good luck-