I have a 2001 Volvo XC70 whose engine has just started to stutter intermittently. you can feel the whole car shudder lightly when this happens. the shudder/stutter is accompanied by an eggy smell. anyone?

 

The eggy smell will be your catalytic convertor.
May be clogging up or you may need new o2 sensors.
Get your fault codes read. That should give an indication of possible problem.

 

It's likely that you electronic throttle body needs cleaning. Because Volvo uses a crankcase ventilation system that pulls vapors from the crankcase back through the intake, the throttle body get gummed up with residue. The radiator fan housing must be removed along with some other parts and then the ETB must be removed. There a good videos on YouTube. Clean out the little air box attached to the crankcase. The car will run 100% better with a clean throttle body. The engine is running rich and the bad fuel/air mixture is causing build up in the catalytic converter. The converter can be damaged because it overheats when the fuel/air mixture is too rich. You should also check the Oxygen Sensor because that can also affect the fuel/air mixture.