Volvo Repair: bucking and shaking at idle no run. fuel pump repair cap rotor, fuel pressure regulator, amp fuse

Question
89 245 auto. month ago exhibited main fuel pump failure. i.e. occasional non start and loud buzz at pump. after week of symptoms it failed to start. checked fuses etc tapped on pump, no start. towed to shop( midas) and after checking they said it was something other than pump. electrical, so it went to auto electric. next day they said it WAS pump, replaced it and filter, and i was on my way. few days later i started hearing in tank pump making loud noise.  while at friends , i changed dist. cap for aftermarket one. on way to shop for scheduled tuneup car was bucking and hesitating. made it to shop. in tank pump changed and all was said to be well save for 2 fuel trim (?) codes. on way back home at 60 mph car exhibited same hesitation and slight bucking. appt to see shop in 2 days was made. never made it.  i replaced distributor rotor . car ran fine on short test. so went on ride to friends house. going uphill car started that hesitation, bucking low power thing again. died in friends driveway. restarted with horrible shake of engine. low power and pop or ping in exhaust. don't know if connected, but i did smell rubber burning while going up this hill. the fan belt had been squealing all fall.  towed to shop now. ?

it started with bad pump. only thing that i can think is it's somehow connected to my changing the cap or rotor. it seemed to run okay before that. though at same time the in tank pump was going. i know fuel relays and 25 amp fuse sometimes go, but haven't checked them. shop said they were okay. can cap and rotor problems cause all this?  

Answer
cap and rotor would not usually be an intermitent problem like this.it could be a bad air mass meter.I would also check there is no fuel coming out of fuel pressure regulator vacuum hose side.I have seen bad pressure regulator cause poor power they leak inside sometimes.I would try to find a good volvo mechanic or try the local dealer even if they just diagnose it and you fix yourself.