No, probably not. It's probably overcarbed. It's hard to guess, but it sounds like the pressure was turned up and the keg was shaking? If so, it's overcarbed.
Another thing to consider- if it's "sour" it's probably a lost cause. But if it's "tart", it could very well be a carbonic acid flavor that comes from trying to carb the beer quickly (say, with higher pressure than serving pressure, and/or shaking, and doing it in a quick amount of time).
I'd stop messing with it, and set it at 10 psi and leave it alone. Try it in a week to see if it's improved. It probably will be.