had the same prob a couple of months ago on my nissan truck, took my mechanic 2 weeks to trouble shoot it cause everytime he would put the scanner on it it would fire up again(really messed with him)ended up being a corroded plug at the batt terminal that was the main power for the computer. had fuel press at the rail, had spark, would run when i would dump fuel into the air body.
look at those plugs, might be the problem
jason