to biglow or other HH, about car stall problem

last time the check engine light stay on and it was misfire, changing the spark plug and wire the car run well again. so is this the real reason of car stall intermittently? the dealer said they did the two tests you mentioned, it was fine. they kind of want to get rid of us, ask us to pick it up. but I am worried that it will happen again since seems we didn't find the real problem.