I have a 2002 S80 T6. Just the other day while driving the engine seemed to drop to 2 cylinders. I pulled over, tried to restart. It would start, rev for a second then drop back toward idle and it felt like 4 cylinders had dropped out. Smelled a rotten egg gas smell as I was trying to get it going.
Recently had plugs replaced as it had started to take a bit longer to crank over cold (4 to 5 seconds). Had it towed to my mechanic who is a bit bewildered. The messages he is getting are saying that 4 coils have failed. Is this possible simultaneously ? He doesn't think so and is thinking it might be an ECU problem. Again does the ECU fail in this way. Has he maybe done something wrong when replacing the plugs ?
The car has done 140 kms, had good service and has run perfectly until this event. I did a 300km highway drive the previous day. No problem.
I have seen other similar scenarios posted so this must be a common problem.
Can anyone help please.

 

There are no codes that say a coil is out. He probably has 4 (or more) misfire codes. If he doesn't know how to fault trace a misfire, look for a new mechanic. It is easy to check to see if each coil is firing and that should be done first