Engine will not stay idling

I can get the car to start if I hold accelerator to the floor. Once started will only stay running for a few seconds not even a minute sometimes backfires. I bought the car from a friend. It had sat about 5 years. Previously when driving down the road the car would shut off even at 80 MPH, I could turn the key back for 3 to 5 seconds and turn it back on without any problems sometimes. Sometimes I would have to do that multiple times. The last time I drove it, it did the turn off thing I was on a hill so coasted to the bottom until I tried to start it when I started it the whole front end rattled and shut off again. Now I'm at the beginning of this chat.