Looking for advice on problem with High Idle. Background: have a Dodge 2006 2500 Ram Diesel 5.9 Cummins, with Diablosport Predator tuner installed by the previous owner. (130,000 km/80,000 miles) In February, it all of a sudden started to idle high (for no apparent reason). Took it to our mechanic, and he changed the tuner settings from Tow Mode to Performance, but that did not seem to do anything. Seems like the truck is going to take off when idling at a red light. Revs when I change gears. Is there a way to stop it from high idling? If I take my foot off the brake, it actually accelerates forward on its own for a couple seconds, then slows down. My wife refuses to drive it, she is so terrified of it!

 

Not sure about the 2006, but maybe try rotating the TPS slightly. It has slotted holes to allow for adjustment. Or maybe the TPS itself is going bad.
Let us know the final fix.

 

I would get rid of the tuner all together to eliminate that first.