Hyundai Repair: 95 sonata, vacuum leak, fixing cars

Question
i have a 95 sonata 2L auto went 2 start it about 2 months ago started fine then it reved up to 3500rpm back down to 1500 over and over and over idles fine with load on it (when in gear) i live on fixing cars so did what most would tryed to fix it and two months later here i am   no check engine light  took it to dealer no codes ?????? they wanted 60$ a hour to try and fix it  but no guarantees i have no problem doing the work just need a place to start   ps    please help me

Answer
Usually, this rpm fluctuation indicates that the idle is too high and the computer is unable to lower it by controlling the amount of air entering the engine.  The fluctuation occurs as the computer begins shutting off and reenergizing the fuel injectors in an attempt to control the idle.

The typical causes are as follows:
1.  Vacuum leak allowing extra air to enter the engine.
2.  Faulty idle control motor.
3.  Improperly adjusted items on throttle body.