You can send it back. Try a different room in the house. Take it back to the store. It could be because of interference from the kitchen or computer or TV or something like that. Also, those cars only have about 5-8 feet of range out of the box. So, if it's father away than that...that could be the reason it stutters or stops.
You need to have some soldering skills to replace the antenna in the car. I would use 24g solid copper wire or cat5 cable.
You could also try the crip cap mod which is at
QFM and also posted somewhere in these forums. Do a search. : )