93 Toyota Cor. the car wont start up after it shut off?

93 Toyota Cor. I was driving and down shift to 2nd gear the car was loosing its powers and then I move it back to 1st gear because I felt the care was getting ready to cut-off. Once I move off the road it shut off. Change the TPS and still it won't start up and keep running. Also, change the spark plugs nothing seem to fix the problem. What could be the problem?