Pennsylvania's exemptions are somewhat on the low side and so you should opt for the federal exemptions. The federal exemption for a motor vehicle is $3,225. However, there is a wildcard of $1,075, and, if you do not need the homestead exemption, there is additional exemption available from that category of potentially up to $10,125.
HOWEVER, this answer is based only on the very narrow question as to your $7,000 car. Bankruptcy requires full disclosure of all of your exemptions, and, depending on the extent and nature of all of your assets, these exemptions may or may not apply in your case. For that reason, my opinion is that to do a bankruptcy without legal advice would be fairly dangerous.
This answer is provided for informational purposes only. True legal advice can only be given in an office consultaiton by an attorney licensed in your jurisdiction with experience in the area in which your concern lies.