Help, when I get into my 2004 mazda6 ts 136 in the mornings the rev counter often keeps dropping to the bottom and stopping the engine. This happens in the first half an hour of driving. After that it's fine. It would happen for example if I slowed down to take a turn off from a main road.I change down to second gear and the rev tick just drops, and there's me deperately trying to start up again.Afterabout half hour is up the car drives like new. Does anybody know what that could be? There's 70,000 miles on the car also.