I'm like you Tim. I don't work on modern engines.
I think Jerilynne is on the right track. The idle is controlled by a computer. The sensors tell the computer what's going on. A bad sensor will give the computer the wrong input. The MAF sensor is the one that goes bad more often but there are other sensors on the exhaust manifolds and catalytic convertor too. I think a MAF sensor costs less than having a technition ( remember when they were called mechanics?) hook it up to a diagnostic computer. Or it might just need a new air filter.