Hyundai Repair: stumbles, sonata, hesitation

Question
My sonata stumbles when I turn on the a/c.Worse at idle.Dealer couldnt diagnose/fix it.

Answer
Hi, Larry.  I'd like you do provide a little more description of exactly what your car is doing.  Try to tell me what you hear/feel/see that makes you think your car is doing something abnormal.  "Stumbles" usually implies a momentary hesitation when the throttle is applied, followed by normal operation.  Since you say it occurs at idle, that makes me think you're not referring to the symptoms I've described.

Also, please tell me the model year of your Sonata and what engine it has.

Lastly, what did the dealer tell you about the problem when you took the car in?  Were they unable to duplicate it?  Did they determine it was normal?  Did they concede there was a problem and they didn't know what it was?