Hyundai Repair: un stable engine, valve stem seals, head gasket

Question
dear sir
i have huyndai-elantra-1994 automatic trans. 1500hp , the engine i un stable and to much smoke , i checked the timingcase ring and centerd it was ok please help me thank you verey much.

Answer
Smoke usually indicates that you have coolant or oil leaking into the cylinders.  This could be due to a problem with the valve stem seals or the head gasket, or could be due to a major engine problem.  

If the problem causing the smoking is also causing a misfire, then that would explain an unstable idle.  

I'm not sure what you mean by the timing case ring, so I don't know the significance of reference to it.  Hyundai didn't offer the Elantra with a 1500cc engine in the United States, so there's a possibility I may have no specific information about this engine to give you.