Impala Stalling

My son has a 2000 Chevy Impala with a 3.8L V-6. It has a cronic stalling problem! The car will be running fine, for months, when without any warning it stalls out. Generally, it stalls whenever the engine goes to an idle, such as when coming to a stop or when coasting or the engine is under a no load situation. This is very dangerous when driving the car and making a turn and the power steering fails, since the engine has stopped turning. Each time this has happened we’ve checked the OBD, but it DOES NOT give us any fault codes since the MIL (Malfunction Indicator Lamp) does not come on! We’ve replaced the crankshaft sensor once, the MAF sensor once and AIS motor twice now and the ramdom stalling has remained. Sometimes it will clear itself and drive fine for 10 minutes or for months. All wires and connections have been checked and all are good. Does anyone out there knows what’s going on with this car?