I have a pontiac grand prix and I installed a sound system on it and started having problems like it would die on the stop light only when I had my music up loud and then it took a while to get it to start it takes about 4 min until it starts again may be it's the battery to small but the battery doesn't die

Those big sound systems require larger output alternator and battery.

i have a pontiac grand prix and i installed a sound system on it and started having problems like it would die on the stop light only when i had my music up loud and then it took a while to get it to start it takes about 4 min til it starts again may be its the battery to small but the battery doesnt die

Sounds like you are drawing too much power away from the charging system. A telltale sign is when you have the car at a steady speed, at night, with the headlights on. If the stereo is up and the headlights dim, you've got a power drawing problem. You need a higher amperage alternator, a heavy duty battery (like an optima or diehard) and a capacitor. That way you avoid overtaxing your charging system.

In any case, make sure that all your wires are secured, with no pinching, and that you are using the correct gauge wire for your application. Also, make sure that everything is ground correctly.