My advice - don't get a loan. Seriously. Pay cash even if that means waiting a while. If you don't have the discipline to save up first then what are the odds you'll be able to make payments in the future? Few things mess with your life like having the bank repo a used beater, sell it for pennies, leaving you with no car and you still owe them money.
Seriously. DO NOT FINANCE A USED CAR. Especially those, which obviously have problems.
Drive a beater until you can pay cash for a *nicer* beater, then drive that until you can pay cash for an even nicer one... Do that for EVERYTHING, your tv, your stereo, etc. You'll end up financially stable and pretty well off a lot earlier. My parents did this on a crap salary with 4 kids, and although we lived cheap for years, we never had money problems, never went hungry, never had bill collectors banging on the door, and my parents could legitimately promise to send all 4 of us to school. Before we moved out of the house, we had real cash to spend on anything we wanted and I get to live my life knowing I won't ever have to financially support my parents. My kids won't either, because we never buy anything on credit either. Our house mortgage is the only debt we have and that means with no car loans and no credit debt, we have around a $1500/month advantage over everyone else because that's about $1500 everyone else spends on cars and credit cards that we have as real cash to spend on nice things, save for future expenses, go on vacations, etc.
Don't start deficit lifestyle now... Save cash and buy when you can pay cash for your hoopty upgrade.