Kaln08

Audi s5 misfires

I have a 2015 audi s5 b8.5
Last week while going down a hill I shifted into a lower gear to engine brake and the EPC light came on. After that the car would shake under load. I pulled over, shut it off and waited a couple minutes. When I restarted the car the light went away and the rough idle went away. I assumed it might have been a clogged injector, the pump had sucked something up under increased load when the RPMS spiked from down shifting and then when I shut the engine off and the pressure released the obstruction cleared itself. But today while my wife was driving it the check engine light and the epc light came on and the engine began to shake again. The check engine light was for a cylinder 4 misfire and an high rpm code. I replaced the coil pack and spark plug (easiest and cheapest fix) which resolved the misfire. However the check engine light is still on and now I noticed the exhaust is thick and smells sweet. I know what that normally means. I am really hoping it's not a head gasket leak. Which it could be, it could be leaking coolant into cylinder 4 which cause the air fuel mixture to be off and cause the misfire. I just want any second opinions before I start tearing the top half of my engine apart. Any ideas?

The car has 130k miles and no warrenty.

hahnmgh63

So no other fault codes than #4 cylinder misfire? Any change in the Coolant Reservoir level? How did the plug you removed look? The fuel filter does a pretty good job so I doubt something got by it to plug an injector. A leaking headgasket is usually real noticeable right at startup as Coolant pressures after shutdown push coolant into the cylinder but it sounds like yours was at a little higher rpm when running?

Kaln08

It had 2 codes. 1 for cylinder #4 misfire and the 2nd code was for high engine rpm. My coolant reservoir when cold is at the min level, when hot it drops to about an inch left in the reservoir. I have not noticed a drop in levels in the past week. The spark plug was dirty with some carbon but it wasn't wet and didn't have any ashy build up. I haven't seen any coolant in my oil or frothing to indicate coolant is leaking into the block. Could it be a valve cover gasket? I have also seen threads about the supercharger core lleaking causing a misfire but that normally causes cylinders 3 or 6 to misfire, not the forward cylinders.