ok so we have an 07 expedition max limited with the 5.4l. This morning when my mother started the truck, it started fine but when it was left for a few seconds all of a sudden it started idling like a dragster!!! It stays around 1000rpm mark but its jumping around and sounds like it is almost bogging out at some points.

please reply if you have any ideas what could be wrong or this has happened to you.

thanks

ps. the drive train is bone stock

 

MAF sensor? It's between your air filter and throttle body. Without getting the codes read I would start there.

 

Sounds like it jumped timing.....Could be the computer or the timing belt.....just a guess!