Volvo Repair: P0301 code and rough running, volvo vadis, cap seal

Question
car is 99 s70 glt sudde4nly it started running too rough to drive it was perfect till then check engine light came on. code was p0301 when I erased the code it would no longer start. until I erased the cfode it started every time it was just too rough to drive maybe running on 3 cylinders or something.

Answer
Thom, you cant use generic scanners on the 99-present day Volvos.  They require the Volvo VADIS computer system.  Sounds like you are having coil pack issues.  Check all spark plugs while you are there.  I have seen the oil cap seal leak into the holes and fill up with oil.  Could be the problem there.  Roger