My daughter has a '99 626 ES that is having problems with the idle surguring. Car has 125k and has been well maintained. Surge is most noticable with the a/c on. Idle will vary from normal 750 range to as high as 1800. Does not generally go below 750 though. Surge happens in gear or while sitting in park. Any ideas? Idle Air control valve maybe??? Thanks in advance for any ideas.