I have a girlfriend with a 99 F-150 and it has a miss. I put new plugs in it a couple a weeks ago and it cured the problem. But now it has come back, I was wondering I usually work on Chevy's and does Ford have a close loop and open loop setting in the computer? I was trying to figure out it her 02's or MAF censer was bad? The SES light is on but was just trying to figure out any trouble shooting I could do.

 

My 99 f150 had an o2 sensor go out about every 45,000 to 55,000 miles. Have you cleaned out the throttle body, mine used to get crud in it allot but it might have been from the K&N filter but they do recommend cleaning it every 3 to 7 thousand mile. Use the cleaner that does not harm the coating of the throttle body though. Other than that mine seemed to have a small miss allot and runs rough around 2500 miles after an oil change. It will tell you when it wants its oil changed. Lol

 

what plugs did you use??? and what did you gap them to??