you can constantly renew the import papers of your car.
As for having it confiscated, it happened to us once : an attempt to confiscate it at the boarder. there they said we can't get the car out of the country
because we have a DNI. We left the car at buquebus, and rented one in Uruguay.
maybe you can get advice on what to do at
Argenmove, they do our car, and they know the laws.