Volvo Repair: 1992 940 GL Volvo Idle surging, mass air flow sensor, air flow sensor

Question
I have had numerous repairs done on the car these last 5 months:  new radiator, replaced transmission, new tires, new fuel filter, plugs, & wires.  Yesterday my mechanic replaced the oxygen sensor because it idled very rough jumping 300-500 RPMS yet at times it runs fine.  It will have periods of normal idling and then surge when I stop at a light.  This morning it was idling so rough that the car was rocking back and forth when I first started it. Yet once it warmed up, it settled down to only jumping 100-300 RPMs at lights. He said that it oould eventually fix itself.  I am at my wits end.  Any ideas?  I love this car and have had it since it was new.  It has been great until this year.  Any help would be greatly appreciated.  Thanks!  

Answer
Barbara, yes, get a new mechanic.  There are 2 possiblities that he overlooked.  One is the Idle speed motor and the other is the Airmass meter or as most techs call it the Mass air flow sensor.  Have him test those components.  Nothing fixes itself.  Thats just a way to brush you off.  Roger