I changed the O2 sensor and it ran perfect for about 15 minutes. Then back to the same old stumbling, sputtering, and stalling. You can still drive it somewhere, but it will probably die twice. I washed the engine, which wasn't very dirty to start, and it ran very good, with only a little roughness. after it dries, back to the same old problems.

Has this ever happened to anyone else? What is the problem?