Can I be sued by a title loan company if I default on the title loan and give them the car, if the car is not worth as much as the loan is worth?

Yes, you may be sued in that case. The loan company is entitled to the full remaining principal balance of the loan. The car secures the loan, but represents only one way or method to pay that balance; the loan company does not have to accept the car as payment in full. If the car is worth less than the remaining amount of the loan, then after the car is repossessed or taken back, they may sue you for the excess.