The 3.0L and all other commonn rail diesels are not suppose to ilde but I do not know exaclty why that is. Driving around the block or being able to "up idle" by using the cruise control setting as was the case on other diesels that I have owned is just not a feature on the 3.0L. Perhaps Sprinter owners can share what the verbage says in their new Sprinter books. In my 3.0L jeep book it is bold to not idle period.
Go to Google and search for something like "does idling your car engine for long periods harm the engine"? You'll find, as usual, a fair amount of discussion, but I think you'll find the majority view is that it can hurt the engine, the catalytic converter, and the environment. My memory of the military is that the one exception are the big multifuel trucks which are better off if left idling rather than being shut down for short periods of time. The most reliable of these answers probably come from people like Click and Clack on NPR or other practicing mechanics. Check it out and see what you think.Jerry
This is what I found on another forum concerning the "high idle switch: and I quoteAnother option for the Sprinter is the OEM, "high idle" switch. Something that is included in all semi trucks, where you can idle it up.The Sprinter option takes it to a prset 850rpms. It is most common on ambulance conversions, and those using the truck for other commerical purposes.I believe the pricing on it is about $850.00 amd needs a dealer install, because it alte[/color]rs the ECM program. [/font]" So that should settle some of the questions?