Bluetooth paired but audio not streaming from certain apps

Iphone 5s, iOS 7.0.6

This problem only started in ios 7, iphone 5. Wasn't a problem with iphone 4 and prior OS.

The iphone is paired correctly to my car audio system, and the ipod music player works great, the Spotify app works great, and streaming audio from Safari, Netflix, and some other apps works great too.

However, audio streaming does NOT work from the Youtube app, the crackle app, and some others. These apps never had trouble with this same car setup in previous ios.

When playing media from these apps, there is no sound. The phone shows that my car blootooth is selcted, and the car shows it is corrrectly paired to my phone, but no sound coming out of car speakers or phone. Switching over to one of the apps that does work, suddenly sound commences through car speakers. Occasionally, you will hear sound from one of these apps for a split second, before the music player app, or spotify app takes over it, automatically. It's as if the music player apps are taking over these very specific other apps for some reason. Really annoying and confusing.

In my old iPhone 4 with the same exact car, everything worked all the time. Whatever audio was coming out of the iphone, from whatever app, it would come through the car speakers via bluetooth.

Any fixes?

Also, turn-by-turn directions in Apple Maps does not stream audio to bluetooth..why is this? Siri will be talking to me through the car speakers as normal, and the second the directions start, it comes out of the physical phone, not the car speakers anymore. Huge design flaw imo.

Thanks.