3.3 engine cutting out

i have a 99 Plymouth Grand Voyager, 3.3, with 96,500 KMs on the clock. the idle speed would just drop to nothing and the engine would just die, and the 'check engine light' comes on. Happens when you get off the highway and sometimes at red lights. Had the EGR valve replaced, the Fuel Filter replaced, and the throtle body cleaned. my mechanic can't find the culprit. appreciate anyone who would spend the time and effort to reply.