Hello I own a 05 Chevy 3.4liter and I've been having some trouble with the starting and also a shakiness while driving. I have to try to crank my car about 3 or 4 times before it starts. It turns over but doesn't crank. I can't let it get below a quarter of a tank because it will cut off as if I don't have gas. The check engine light is on and it is the 00071 or the code for vacuum leak, fuel filter, which has been replaced. And others but this problem is driving me crazy! Please help.