Wife reports a stall. When she tried to restart, just gave a whir first time, then started but she had the feeling engine/car not running well. I got in the car earlier and when the key is turned to ignition I heard a louder than normal whistle in the cabin. Looked under the bonnet and put my ear to the engine and this electric or electronic whistle seems to be coming from rear of engine towards the cabin. Any ideas what might be up?