2002 Alero having troubles



I am deployed to kuwait and my wife says that recently our 2002 Oldsmobile alero with the 2.2 ecotec has started having troubles. While idling at a stop light for a minute or so the idle drops down to ~500 rpm then back up and continues fluxuating back and forth, she says it seems like it is going to stall. She has also told me that on a few rare occasions the same thing has happened while driving up a hill, the rpms drop and she looses power. She dropped it off at a local shop and they told her, her transmission was dirty. The also said they weren’t getting any fault codes. The car has 62,000 miles on it and has had all of its regular services. She doesn’t feel that they are steering her straight and was wondering if I could come up with an answer for her.


also it has an automatic transmission