I just replaced my price pfister shower diverter with a brand new one and still having the same problem that half the water is still coming out of the bath spout, what could be causing this problem?

You replaced a three knob shower valve with the same thing. Correct? You might have some trash in the diverter seat that's not allowing it to close. Try this.
Remove the diverter stem and check for trash. Now turn the water back on to flush out the seats. Reassemble and test. Better now? If not click on back with all the details you can give me about the new valve. Good luck. Tom