I have a 2008 S40 2.4i..I don't have this issue all the time. Maybe once a month or every other month. When I'm driving in the neighborhood going 30 MPH. The RPM surge up and down the engine acts like it wants to stall. It happened this morning when I was pulling into my driveway from taking the kids to school. I never go over 20-30 MPH because of school zones at the time. It seems to happen only in first and second gear. These episodes have happened in the afternoon, too. So I dont think temperature has anything to do with it. My car has all the scheduled maintenance done and oil changes.
Is my transmission eventually going to go out or could it be a failing ETM?
The Volvo dealership has looked at it and said there is nothing wrong. Seems to be more worse each time.

Thanks.

 

Oh and I must mention I never had a failure light come on ever. Just the regular maintenance msgs.

 

Sounds like either a sensor on its way out or a vacuum leak. Do you get a check engine light when this happens?

 

No, I don't have a chk engine light that comes on.

 

There is a youtube video showing how to clean the ETM. From what little I've read it seems to be a problem area when dealing with surges.