For a while I have been having a problem with my truck. The check engine light comes on intermittenly and goes off in a few days. I put my truck in the shop at the dealership and they claim that the computer didn't pick up that the light has ever come on.
Here's my problem: whether or not the light is on, upon start up, the truck will rev up and down, fluctuating between about 750-1500 rpms and keep revving up and down, back and forth, however you want to call it instead of staying at one rpm. Think as if I were pressing the gas and manually revving up the engine, but instead it's doing it by itself. When the truck is running fine, it usually will idle in park at about 500 rpms. Also, when I am driving at a steady speed, the engine will rev up as I am drving. For instance, if I am drving 60 mph, the typical rmp is around 1500. However, it will jump from 1500 to about 1700/1800 and back down again. And when I am slowing down to stop, the truck will rev up and lurch me forward and will also jam into gears when I am switching between drive, park, reverse, etc because it's running at too high of rpm.
Help! I love my truck but it's been in the shop twice and no one will tell me what is wrong.
Is your truck consuming any unusual amount of oil? If it is, the gasket on the bottom of the intake manifold is leaking causing very high idle at startup and when warm. See any smoke when you first start it up?