Hyundai Repair: Engine Light, poor gas mileage, emission system

Question
I have a 2001 Elantra with 59,000 miles.  Since I purchased it the engine light has gone on and off and I have taken it to the dealership several times to fix.  After each fix, the light goes back on and the engine normally experiences poor performance.  Late last year the performance suffered greatly when the car was almost undriveable due to loos of power.  I took it to the dealer and it was fixed.  Two months later light back on and poor performance and poor gas mileage.  Also, everytime I fill up, the engine is hard to start and the motor must be revved for a minute or so so it won't stall.  I'm past the 5 year warrant for the emission system back I feel that the problem has never been completely resolved.  Any ideas?  Thanks.

Answer
Anytime the check engine lamp is on, the first step is to check the trouble codes.  This will give you information regarding what the engine control module (ECM) saw that prompted it to turn on the check engine lamp.  

If you've got difficulty starting the engine only after refueling, I'd primarily suspect that the purge control valve is stuck open.  This will usually trigger a check engine lamp, but typically doesn't cause a performance issue once the extra vapors are burned off (which you're accomplishing by revving the engine until it won't stall).  

If you've got the same trouble code you had prior to the previous repairs, then you've got a good case to claim the issue was never resolved.  If that's the case, request the dealer to ask for assistance from Hyundai because it's been an ongoing issue from when the car was within the warranty period.  If the trouble code is different from the previous repairs, then there's likely no relationship between the previous issues and the one you're having now.