first off is there such a thing?  here's the skinny...
 My wifes caravan finally died, we went to numerous used car lots in search of something we could afford to make payments on. anyhow we found a car after test driving and  coming to an agreement with the car lot on financing and payments.
before we even left the lot the check engine light came on, they scanned it  and said it was nothing... the next day I took it back in and they sent me to their mechanic, I dropped it off, a week later they call and say it's fixed. so we pick it up and before we get home the check engine light is on again! so back it went...  they still have it.  we bought it 27 days ago, we have had it only a few days... and we have made two payments on it already.( we have to keep our credit good) .
so what are my rights regarding this? they gave us a 30 day warranty, it's goping to expire by the time I get the car back and we havent put 50 miles on it yet.   and before you ask...I tried the pleasant conversation route twice, the last convo was a bit more heated...and I'm sure this next one is going to push me mad!

Update 9/21.. so after dropping the car off on the 6th of sept, we called about it on the 12th and were told they had to order a MAF sensor. so we called again on the 19th to inquire where the hell our car was...we were again told they were waiting for a MAF sensor. well they called yesterday on the 20th and said it was ready! we picked it up and drove it home with no check engine light! well.. this morning my wife got in it and was driving to work and the light came on again after driving to the lot to speak with someone .. we are once again dropping it off  to get fixed.  we talked to a lawyer that basically said we could drag it out in court.. but we should just play the game until they fix it.  so tomorrow marks the 3rd payment we will have made... we bought the car on august 18th.. and we have had it in our possession only about 8 days total... I need a shot and a beer

SC Lemon Law

SC Lemon Law FAQ

I don't see anything pertaining to used vehicles, so you may be out of luck.

thanks, ...yeh after reading it appears I may be fooked.  we have never bought from a used car lot before,  usually private party.  I'll have to continue to look for something...there has to be some sort of protection buying from a car lot.

Hey, give me a call.....I may be able to help with it.....after all, I do it for a living...

I went through what you did, but i got my money back. Used grnd cherokee from fennelis off 199b in summerville. I didnt even make it to my place on james island before the upper radiator hose blew. Put a new one on. The head gasket was leaking. Called them up to get my money back salesman said sure. The owner said different. Paid for it full in cash. They told me their interent was down i wanted to borrow their computer to insure it before the drive home. So i waited for them to tow it back with my 40$ in gas in it cause they gave it to me on a quarter tank, my upper rdiator hose. So they said if we fix it do you still want it. I said yes. Well the owner decided after they got it to their shop a few days later to give me a check for my money back. So i was out 40$ in gas, 16$ for upper radiator hose, and get this towing back to their shop which would have been free if i had it on my insurance. Owner tried to bully me over the phone i told him id come up there and talk to him. Well someone cut out the check engine light and a few other lights. Two weeks went  y they had it back up for sale for 900$ more than i paid they threw a roof rack on it. Im sure if you go up there and raise hell youll get your money back.

I would put all of your requests in writing and have it delivered via certified mail to the dealer.

Don't be afraid to demand 30 days warranty after they repair your car, or your money back if they don't fix it.

File a complaint with the Better Business Bureau if you are not satisfied.

Having your issues in writing will help build the case in your favor in case you have to go to court.

updated OP... and life still sucks...

Have you contacted the SC Dept. of Consumer Affairs?

Are you able to take it to your own mechanic for another assessment of the repairs needed to get it back on the road?

The car dealer might not be telling you the complete story on what it needs done.