Has anyone else been having trouble with their engines idle reving up to 1100 RPM's by itself? You turn the engine off and turn it on again and it returns to its normal range of about 685 RPM. The dealer says there is nothing wrong. Ideas anyone?
Yes. This is normal. The newer diesels have a sophisticated emissions control system which essentially "traps" particulates and later burns them off. When the engine goes into a high idle setting, it's the engine going into "re-gen" mode where it essentially super-heats the particulate trap to burn off the soot. This is normal on the '08 6.4 Power Strokes. I don't know of any way to defeat it. I wouldn't worry about it.
What kind of mileage are you guys getting on your 6.4s?