hi i have a 4litre Auto Which has been fine untill yesterday it has power up untill it hits the 3rd n 4th gear and it quickly changes from second 3rd into 4th quickly and if crusing along at 50 i put my foot flat to the flow it does not kick down it just slowly picks up speed it seems to be idleing high to around 1500 rpm as i rev it up it slowly comes down and then takes a while to drop back to 1500 rpm or if not 2000