So this morning, upon start up, after a few minutes my idle started to climb rapidly in the manner of a runaway diesel. I shut the car down, waited a few moments, and drove the car off (82 300sd) and then parked with the car at a normal idle. Again, the idle began to climb rapidly (only in park) what gives? It does ,for the first time, a tank full of bio diesel (versus diesel) and has been running great on this . . .could this have anything to do with the runaway idle? What might cause this situation, help! Thanks!