Datura gives horrendous visions, think the floor turning to spiders and seeing ghosts and zombies of people you know everywhere, muscle spasms, seizures, death etc.
I've never, ever heard of a person successfully killing him or herself this way.
There's a Catch-22 here, in that the methods that leave you unconscious taking pills or sucking car exhaust also leaves the possibility that someone will find you and rush you to the hospital.
And at the same time we may feel partly guilty that it was our fault, our negligence, our failure that contributed to it.
Odds are you also haven't yet.