rpms go up and down when idleing

The cause of an idle surge can sometimes be hard to pinpoint. A sensor could be failing but not enough to turn the check engine light on. You may have a dirty throttle body or a fuel injector issue. This problem may need to be checked out by a qualified technician. If you don't have a regular shop that does your repairs check out the listings at www.repairpal.com.

I had the same problem with my car start about 2 months ago and thought it was the O2 sensor as well, but it turns out it was the mass flow air sensor instead.