Volvo Repair: volvo 240; stalling problems, 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 newer models; so if you'd rather refer me to someone else; that's ok too.

help!

ed

Answer
Thats a difficult one.  The loss of power, or the engine dying shouldn't be that hard to find, but it raced?  I can't imagine what could cause that car to do that besides the gas pedal sticking.  If they are related I can't come up with a cause.  As for loss of power, possible causes:

1- improper metering of air
   ex. vacuum leak, malfunctioning air meter,
2- reduced air intake
   ex. plugged air filter, air inlet clogged
3- improper fuel metering
   ex. clogged fuel filter, clogged fuel lines, failed
   fuel pump, clogged injectors/carburator
4- improper exhaust measuring causing improper computer
  outputs
   ex. failed O2 sensor, failed O2 sensor heater element
5- bad cylinder compression
   ex. loose engine tolerances, timing belt off 1 tooth or
   more
6- engine misfire
   ex. preignition, detonation, fouled plugs, improper
   air fuel mixture

My suggestion to you though is talk to the dealer about a flight recorder.  In extreme situations the dealer will install a flight recorder in your car that will record all your computer information as its happening so when the lack of power occurs you just hit a button and its stored so a shop will know what is going on with your car.  Hope that helps.

James