car dies while coming to a stop on 2000 Nissan Altima

my car dies coming to a stop, or turning or going down a hill. i have taken it to a shop, and seems no one can tell me what is wrong with it. i have had tune up , and the car has been taken pretty good care of.

Asked by for the 2000 Nissan Altima
Your car has on board diagnostic capabilities a professional grade scantool can look for stored trouble codes and pending trouble codes in the compputer that controls the fuel and ignition system in your car. Key engine sensor values can be looked at as well on the scantool without having to do intrusive testing at various sensors in the engine. You have "tuned up" the engine, did you get the mechanic to drive the car with you and point out the staling issue to him? It should be simple to at least for them to offer an opinion as to what may be wrong. I suspect a vacuum leak at the intake manifold or idle air control/idle speed control system.