hi, i’ve got a '96 volvo 850glt - it’s a sedan. i’ve had tons of small problems, and about a year ago the transmission went out. as i live in chicago, there was no rush to have it repaired. well, i finally did take it into the shop, and ended up having it rebuilt.
unfortunately there are still some problems. when at low rpms - under 1.5k the engine wants to stutter and stall. it’s an intermittent problem, and usually not there at all, but when it is, it happens most often when i’m at a complete stop.
if i tap the gas pedal a bit, and get the rpms up, it’ll go just fine. sometimes though i can’t keep it from stalling - if that happens a few times in a row, it won’t start. but if i leave it for a while, it’s fine again. i should add, this is, of course, not a problem on the highway.
anyway, i’ve been told lots of conflicting things - fuel line, fuel filter, spark plugs (all by amateur mechanics). i have to admit i don’t know enough about cars to really have an idea, but i’m hoping to get an opinion!
ps sry for the long post. 
It sounds like you have an Idle Air Control valve problem. This is a fairly common thing to happen. Cleaning or replacement is usually the answer.
thanks!