starts some time or when driving if put in park it will idel down and die

What is your question?

My van will start some times but other times it has like a slow dragging sound I guess not sure rally how to describe it but that is as close as I can when I put it in park it will idel down and die most of the time there is some times it will not but most time it does had it checked and it said it was the knock sensor was bad and my 02 sensor but I have read that it is not always those sensors that r bad anybody have any ideas on who is right ty in advance