1987 Nissan Maxima trouble starting

1987 Nissan Maxima, automatic, fuel inject mileage: 140,000. My car is having problems a few problems. It has trouble starting (whether the engine is cold or not), and also cuts out, like when stopping at a stoplight. Both of these occurrences are random. Sometimes the car works fine, and other times, I've had to get it towed to a service station. When the car has trouble starting, the engine cranks, but doesn't always start. When it cuts out, it can sometimes be started right back up, other times it does not. I've had the fuel pump, distributor, and an electric module replaced. The mechanics also tried switching the airflow sensor and the car's computer, but neither of these worked. Please help! I've been to three different mechanics (including the dealer) and no one knows what the problem is.