Is this what it sounds like when it sputters?
Click me
Cause what you are describing to me is the exact issue mine was doing months before the engine dropped a valve seat. It was giving me a warning and I kept putting band aids on it not knowing it. I replaced the Crank position sensor, pressure control valve, Idle air control valve, and the ignition coil. All seemed to make it better and it would be fine for several weeks and then it would start sputtering again, and stop wanting to start again. Then it would be fine again with me doing nothing to it, then it would go back to doing the symptoms again. Finally one day my wife took me to work, car was fine. She then drove to school, she decided to pull into a gas station to get a pop and the car shut off on her as she was pulling up to a pump. It had never just randomly shut off, she tried to start it but all it would do is crank and crank and crank. She thought it was just going through it's not wanting to start faze again so she let it sit for a lil' bit. Then she tried again, it cranked a few time then finally it started up. but she said it sounded like the engine was grinding and screaming, it shut off again after about 30 seconds of running. It has never ran again.
Just a warning, Good Luck.