Me my best friend and his cousin all have b5's................Just thought I would add that in there.....Anyway my friend's s4 has a random misfire underload at around 3500 rpms. That is the code that is comming up anyway. He has changed the plugs 2 time and has changed the coil packs too. I don't know what else it could be. He said it is also worse when it is hot out. It also does it in chipped mode and stock. Me and my friends came up with dirty injectors? What do u guys think......Anyone else have this problem? Thanks

 

Have you checked your MAF, that could be causing the misfire as well. I had that situation in my 2000 S4. And after changing it, it seems to work fine.

 

Hi !
Mine did the exact same thing "random misfire" and it was EGT sensor.
Engine Gaz Temperature sensor. PITA to change on driver's side but easy
on passenger side. It will show a code for "short to ground... bank 1 or 2", cant
remember exactly what it was though. 200$ + for part + labor, _+1 Hr.
Good luck & keep us informed

 

The F hose was cracked. But he said he was still getting a misfire.