Check fuel pressure. It may be bleeding off pressure while it sits.
January, 5, 2013 AT 8:31 PM
As I recently discovered, another possibility may be the C.P.S.
Cam Position Sensor tells the PCM when to activate the fuel injectors, and is one of the major undiagnosed faults for hard starts and engine stumbles.
Usually you will get a "check engine" code but not always.