My 2008 S40 is randomly misfiring, causing the check engine light to come on. My OBMII meter sometimes shows a misfire with cyl 5, or cyl 3 or cyl 4. It is never just one cyl, it varies. Is there a coil pack relay?? Thanks, Marco

 

coils are just one possible cause of a misfire. Given you are seeing misfires across 3 different coils, I'd tend to rule those out as a possible cause. Other possible causes are things related to fuel trim, including fuel pressure, intake air leaks, and the coolant temp sensor for starters. Another thing to check are the spark plugs. How many miles on the car and when was the last time the plugs were looked at or changed? (should be a 60K mile service item but check the factory maintenance specific to your model).