2003 Volvo XC70 SURGING ENGINE REVS

Any applicable trouble codes? Some of the national brand autostores used to check codes for free. You can call and ask? A code might us in the right direction?

I would suspect a dirty pcv system and dirty throttle plate. You need a pcv gage to check for vacuum and if there is no vacuum then the intake manifold needs to be removed to get access to the pcv hose under the intake. The bolt is like a pcv valve, that will need to be cleaned out, a thin wire will need t be used to clean out the banjo and clear the pcv passage, and most likely the oil tra box will need replacing as well. Once the intake is out, remove the throttle body out and clean the plate. Now if you have potentiometer codes for the throttle, then most likely the throttle is failing. But like mentioned by JDL before, if you can get it scanned an post the codes on here it should help to try and point you in the right directon.