It's been getting in the 40's over night which is cold here in phoenix. When I start it up it starts fine but a minute or not even a minute after- it will start to idle absolutely crazy. Random knocks and the whole car is practically bouncing because of it. Of course, after a few minutes of warming up it is fine and purrs- should I be worried about damage? What is a solution to this? I do not have easy access to plug in the block heater.