It is about 20 degrees outside. Car would not start. Coolant temp sensor has been replaced fairly recently. Code 13, cam sensor signal. Pulled out sensor, cleaned it, car started right up. Another day car hard to start. Cranks well, tries to fire. After cranking several times it eventually starts up. Never acts up while driving and also starts easily after driving. Please give info on possible causes, things to troubleshoot. Thank you.