Volvo: 1991 volvo intermittenly stalls, air filter element, driveability diagnostics

Question
this is a 1991 240 with 132K miles; we bought it about 6 mos ago. had the car checked out by a local volvo repair shop; they said it was a "strong" car and said it should be OK to buy. i paid $2900.

here's the sporadic problem we're having; cant pinpoint a pattern:

this car will run great for days; even weeks; then it will begin to "sputter" and die; often after pulling up to a stop; but it will do this when slowing down too. sometimes; after it dies; i leave it sit for a few hours and then it will start up OK and run well again for several days, or more; out of the blue the problem will happen again.

my daughter was driving it a few weeks ago and said the car started "shaking, or sputtering" and then the engine started "racing" causing the car to surge forward. she was able to park it at her dorm parking lot and hasnt driven it for over a month because she doesnt feel safe. now it wont start at all (i think the battery is dead).

here are the repairs that 3 different shops have done:

1. repair pvc system
2. replace spark plug wires; distributor rotor, cap
3. replace ruel filter; replace engine fuel filter.
4. replace air filter element
5. conducted driveability diagnostics- two shops had this car for over a week each and drove all over the place with no problems.
6. replaced spark plugs
7. replaced rear engine seal

i also put in a new battery;

i bought this car for my two daughters to drive mainly around town and some 4 to 6 hour freeway trip; that's about it.

i realize you specialize in older models; so if you'd rather refer me to someone else; that's ok too.

help!

ed

Answer
This strikes me as a fuel delivery issue.  I would check your injectors for clogs or a malfunction.  I would also check your fuel pumps (both main and in-tank) as well as the relay, checking for constant voltages while the engine is running (making sure they aren't cutting out).  I would also inspect your throttle body.  Clogs and air valve malfunctioning within the body can cause issues like what you describe.  Finally, I would check the mass air flow sensor;a malfunction here can send the wrong throttle information to the computer, causing it to surge and/or die.  Good luck!