During the last two months, in one 1 out of 4 cold starts, the engine has started right up, but has not gone into its regular faster cold idle. Instead, immediately after starting, the engine goes into its warmed up low idle and runs rough. I have to press on the accelerator for a couple of minutes to keep the engine from faltering until it warms up a little. The faster smooth cold idle never comes on. When the engine is functioning normally, it starts right up and runs evenly at a slightly higher idle until the engine warms up. In the last few days, the problem has been occurring more often, in 1 out of every 2 starts in the morning. Could the device that senses and sets the idle be failing?

Other information: About 3 years ago, Volvo installed/downloaded the latest starting software so that other than with this problem, the engine starts up right away and runs great.

I would appreciate learning what you think the problem may be and if this is something that is easy to fix/replace or whether it will require my taking it to my Volvo dealer. Thank you.