Volvo Repair: 1990 240 DL Volvo, fuel pressure regulator, vacuum hose

Question
Car had been idling a little rough. Filled up with gas Wednesday of last week, EXXON Supreme. Friday, drove to work...all was well....as I returned home, suddendly, the idling became so rough that it was shaking the entire car,it was as if it were stalling-out, smell of gas like the car was flooded (sp). Thankfully, got off the street into a parking lot.  Smoke was coming out from under the car. The car was backfiring and shaking. Husband came to me.He could not make adjustments...Note: the air conditioning man, working on the air the same day that I had the problem had made "some adjustments," thinking the "idling" problem was from the air conditioning. Yesterday, was able to drive the car home, rough running all the way, backfiring all the way.....HELP.

Answer
Betty, sounds like A/C man needs to stick to A/C.  Im thinking there is a problem with the air mass meter.  I would have you husband unplug it and see if the idle changes.  If it does, have him plug it back in.  If car stalls, then meter is bad.  Have him also pull the small vacuum hose off the fuel pressure regulator on the fuel injection rail.  If fuel is coming out of that small hole, then thats not good and needs to be replaced. Roger