99f250 diesel 7.3 engine light came on,rough idle
(Just a lady, dont know nothing about my diesel. Anyone? Please help.) Ran the truck about 30 miles, ran beautiful. Parked it for 2 hours. Got in it. Engine light came on. In drive, with pedal to floor, only goes to 10rpm's. It was a very rough idle. I let it idle in park as it spit and sputtered. All of a sudden it idled up to 10rpms, dropped down to its regular idle, engine light went off and started sounding good. I hit the gas pedal and got good,regular power. Then all of a sudden it started getting choppy again and the engine light popped on. With truck off, I opened up the fuel drain valve and got some fuel out. Doesnt appear to seperate or have water in it. Does anyone know what it might be?