2000 Chevrolet Blazer with a 4.3 Vortec V6 is very hard to start and seems to be flooding. When the engine fires and starts it is missing bad and runningextremely rough. I am sure that without the excellerator pedal being held to maintain 1000 rpm the engine would die. What should we start with to diagnose the problem or problems? Please advise as replacing parts using the shade tree can be very expensive.