Nissan Repair: 1992 Nissan Maxima shut-off problem, nissan maxima, distributor caps

Question
Thanks for your help in advance.
Vechile Info: -100,000 milage
             -timely maintance
             -changed transmission @60,000      
             (when I purchased the car)
             -changed fuel pump (not OEM)
             -No other mechanical problem

My car shuts off sometimes while idle or in transit.  I properly maintain the vechile and have gone through four mechanics who have checked and changed everything from the Knock sensor to the valve sensor which still has not solve my problem. The last mechanic suggested that the transmission might be goinging, I don't buy that.  The vechile starts right up after shut -off with no problem and runs fantastic on the road.  Any idea what might be causing the problem?
 
                    Thanks,
                            Mark  

Answer
Mark,

Lets make sure the transmission is good so drive the car and once it gets to temperature and the torque converter locks up slow down and see if it dies.  Basically, the lock up torque converter will kill an engine at low speed or at an idle if it does not unlock.  There is a solenoid that controls this.  If you drive the car without the overdrive on the lock up torque converter will not lock and the car should not die.  If the car still dies it is not the transmission.  If this is the case I would look into the fuel pump and the pressure it is putting out.  If the relay is defective it can kill the pump and then when you restart the car the relay makes contact again and you are on the way.  So check the transmission first and then the fuel pump.  Aftermarket fuel pumps are always suspect to me since I have had such bad luck with them.  I will buy most anything else aftermarket.  But, fuel pumps, timing belts, distributor caps and rotors are Nissan only for me since I have been burnt so many times.