My check engine lights has been on for as long as I've had my 1999 ford f 150 and it runs great and has all the power I just don't know what it is or what it could be?

 

Have u pulled the code?

 

If you have an autozone in your town, they will check the codes for free and tell you what the problem is. You can then go about fixing it. It is most likely costing you money in wasted fuel by not fixing it and it could cause even bigger problems in the future. Could be something like an Oxy sensor.