Q&A

It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say. Volvo and a lot of European cars are tricky, preparatory tools, some times a software up grade fixes things. Fist check the basics could there be any vacuum leak between the intake manifold and head or intake manifold/throttle body area. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
You may need a professional grade scan tool to look at live sensor data. For Toyota and Lexus we can test the functionality of the idle air control motor using a scan tool. If a repair shop is looking at your car make sure they have good Volvo experience.