I have noticed when idleing the truck will idle at 700 rpm for about 5 minutes then jump up to 1000 rpm for about 5 minutes then back down to 700 rpm. Why is this ??
2007 6.7 with California style Deletes and Smarty JRME

 

When the ambient air temps are below a certain set point and the engine is cold the truck will engage the high idle feature to help it warm up. This is to prevent cylinder wetting.
Jim W.

 

Ditto Jim W. This is normal for the truck. No worry.