I have a 1988 nissan sentra 70 thousand miles when I reach speeds of 25 mph the car starts to hesitate very bad, my mechanic changed the fuel pump problem remains cleaned and checked all the injectors all was fin put a new distributor in and still the same he now trying the mass air flow sensor? any one have this problem before and have a cure? any help would be of use. Thanks

 

check the fuel pressure regulator

 

Yep, its most likely the FPR, had the same problem with mine.