We bought a new battery last night, and as of midnight this had stopped, but with the old battery in, it was so close to dead it took a great deal of time to start the truck. As soon as it DID start, the RPMS would race up to 1500-2000 at idle. Is this some sort of safety mechanism to recharge the battery? It stops after 5 or so minutes but ten minutes later I was in the mcds drive thru with my foot on the brake and the idle jumped up from normal to 2000 and I almost hit the car in front of me! is there something wrong, or is it just trying to charge the battery? Thanks all.