Girlfriend's 2003 S40 1.9T with 82K, I'm getting a misfire at idle and a slight stumble on acceleration. I now have these codes : P0403 and P0442. The gas cap was replaced recently. I had a P0172 but that was fixed with a new MAS and an exhaust purge valve. I changed the spark plugs (NGK iridiums)and cleaned the throttle body when I serviced it last. I'm not getting any misfire codes. Does anybody have an idea of what I'm missing? I'm new to Volvos. Thank you in advance!

 

the P0403 points to the "EGR control circuit" and the P0442 points to a leak in the evap system. Sounds like either or both has created a vacuum leak. The P0442 can be caused by the vacuum line going all the way bay to the evap cannister (by the passenger rear tier) - that's probably what I'd look at first. You may need to do a smoke test to find it - google "J Tube Volvo" for some ideas.