I haven't had this truck all that long but since it's started to get warm I noticed that when I start my truck it has a tendency to rev up to about 1500 rpms. Does anybody know what causes this because it's starting to make my lifters rattle now. 1997 F150

 

My 99 does that too, the computer does it automatically to get the oil moving.

 

While it is normal for the engine to rev on cold starts it should settle down. Clean your IAC (Idle Air Control) valve.

JMC