Hi i have a 91 integra, when i start the car it runs for 15 mins but not to steady the idle fluctuates, then after awhile i will turn it off then on, then the engine will die. Then after that it will just keep sutting off or wont start until it cold again. I checked the cel light and it is code 4-crankshaft position senor. How do i fix this problem, some please help me.