RS-3 Carbon Fouled Plug (2018 DAZA) rough idle

[fangcatoo]

Hello guys, A few days ago I pulled my 500KM plugs just for inspection because the engine was idling pretty rough, not extremely though, On all cylinders it looked fine but cylinder 3 where the plug had a carbon build up on top instead of white/brownish looking top, the engine is built and I've tried to put a new spark plug in yesterday with no luck engine still running rough, pretty sure it got carbon build up aswell, no fault codes at all, car drives ok but only idles rough, you can feel the vibration in the cabin and also the engine itself vibrates quite abit, RPM is steady. (I do feel sometimes that im getting engine cuts when im cruising at 100KMH at low RPMS)
I've heared it could be :
Bad injector O-RING
Bad Valves (unlikely because I've done a leakdown test a few weeks ago)
Bad/leaking Injector
have any of you encounter this problem in anyway? again I have no fault codes/ no misfires even though at idle you can hear the exhaust pops every few sec.
Engine is built (no sleeves)
JE Piston
JE Conrods
Supertech Retainers and springs
Supertech intake and exhaust valves

ANOTHER STUPID QUESTION, Could a base ECU tune for the car cause one cylinder to carbon foul the plug and not all of them?

 

[thatrs3]

If the plug is fouling, it sounds like an injector. I would start by pulling the port injection rail and keying the car on to build some pressure and see if any of the port injectors are leaking.

Injector o-ring, you would usually hear a pretty loud air noise. So it doesn't sound like an issue there.

 

[Spencer589]

Hello guys, A few days ago I pulled my 500KM plugs just for inspection because the engine was idling pretty rough, not extremely though, On all cylinders it looked fine but cylinder 3 where the plug had a carbon build up on top instead of white/brownish looking top, the engine is built and I've tried to put a new spark plug in yesterday with no luck engine still running rough, pretty sure it got carbon build up aswell, no fault codes at all, car drives ok but only idles rough, you can feel the vibration in the cabin and also the engine itself vibrates quite abit, RPM is steady. (I do feel sometimes that im getting engine cuts when im cruising at 100KMH at low RPMS)
I've heared it could be :
Bad injector O-RING
Bad Valves (unlikely because I've done a leakdown test a few weeks ago)
Bad/leaking Injector
have any of you encounter this problem in anyway? again I have no fault codes/ no misfires even though at idle you can hear the exhaust pops every few sec.
Engine is built (no sleeves)
JE Piston
JE Conrods
Supertech Retainers and springs
Supertech intake and exhaust valves

ANOTHER STUPID QUESTION, Could a base ECU tune for the car cause one cylinder to carbon foul the plug and not all of them?i

I have a similar issue with my stage 2 RS3 daza. About September time last year I had some serious misfiring on a cold start. I tried to drive it a bit down the road to see if it would start firing on all 5 but had no joy, engine management light came on and it told me to take it to the workshop. So I parked it back on the drive and managed to get a diagnostics booked in for 2 days after. I started up 2 days later and it was firing on all 5 but the management light was still on. I got it plugged in and a print out. The bloke cleared the faults and told me to take it for a 5 minute blast he plugged it back in and no faults came up. Since then I've found that it can misfire a bit on a cold start if I don't put it in dynamic before I start up. Not sure if it's because the wastegate rattle delete in the remap wasn't messed with when in a dynamic cold start? But after a thrashing it'll have a slight misfire when idling but not if that's just over fuelling to bring the engine temperature down.

Here's the results of my printout