Ok, my car has been functioning normally up until two days ago. I went out in the deep freeze weather and started it and was in a hurry so I took off immediately. Anyway the speedometer went nuts on me. I had it wound all the way around to 85 and people were passing me like I was standing still plus the speedometer was bouncing between 80 and 85. I got to my desintation, was there for an hour and it was fine after that. Is it anything I should be worried about?