My 1996 nissan maxima is having a problem with idle, hesitation and stalling. With even pressure on gas pedal, idle will drop down and then jump back up, also has stalled. Brought to mechanic and it took a while for computer to recognize problem. They said it showed up as idle speed sensor. Got car back and it happened again. I figure either they replaced with faulty part or something else was to blame to begin with. I have read a few things online that indicate that problem could be air flow sensor. Likely? Also what is block sensor and how would air flow sensor symptoms and block sensor symptoms differ? Mechanic had mentioned that if problem reappeared that it could be block sensor, but I really tend to think it is the air flow sensor. Please help, much appreciated.