Hi MariaT,
Sorry to hear about your troubles. There isn't much you can do about it now, except purchase a warranty if it isn't too expensive.
But I do have some tips for buying a used car. I've worked in the auto repair business for over 10 years and here are some things I've picked up along the way:
1. Have a mechanic check it out. You can arrange to bring a mechanic with you or ask the seller to take the car to a mechanic of your choice at your expense. Sure, you'll have to pay for the mechanic's services, but how does $100 compare to $4,000. Have the mechanic put his/her findings in writing. If the needed repairs are minor, and you still want the car, you may be able to negotiate with the seller to either fix them or come down on the asking price.
2. If you decide to check out the vehicle yourself, take along an inspection list. There is a good one at [url=BellaOnline ALERT: For anti-spam reasons, we restrict the number of URLs allowed in a given post. You have exceeded our maximum number of URLs.