'90 Chevy 5.7 Lt., runs great when engine is wet. Otherwise bad...

[5058885179]

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?

[toivo]

check base gasket on the tbi. they are known to leak and cause problems. spray carb cleaner at the base of throttlebody all the way around and see if the idle changes. if it does it's leaking air.

[5058885179]

that was what was wrong. Also, the fuel pressure is sort of low. How much pressure should it have?