When the car has warmed up, it blows blue smoke out of the exhaust when I take off from a light after idling. It does not blow smoke in the morning when I start it. Plus the check engine light was on. I took it back to the dealer, they told me crap about emissions, eer valve, pump something or another. They supposedly fixed the problem. The check engine light is now off, but no sooner was I four miles from the dealer, it started the with the smoke again. Help, anyone know the problem? I am thinking rings.. valve stem seals.. etc.. PCV? What are my rights buying a used car off a dealer lot? I do have a 3 month/3,000 mile warranty, but they are beating around the bush. I am taking it back on Monday.. any suggestions??

UPDATE: They really had no idea why it was smoking and I could tell they didn't want to dig into the engine and replace the rings, valve stem seals etc at their expense.. so I asked for my money back.. and they gave it to me... no hassle what so ever, can you believe it... Looking at buying a 2001 Chevy Lumina now...