2012 Skoda Octavia 2 MY13; CDAA; EA888 engine weird misfire.

[anotherdownunder]

Car bought at 109k no problems since then. Oil/filter changed every 5km.
At 140k now severe misfire VCDS says cylinder 2. Spark plug 2 very wet.
Change all plugs, new oil, 5-30, air and oil filter; plugs. No problem for around 50km then misfire 2 again. Plug cyl 2 very wet again. 'Cook' this plug on gas stove and problem gone for another @ 50km.
Garage says comp & leak-down tests no good it's carbon build-up, want to decoke with walnut abrasion.
Maybe no 2 injector leak ignored by them.
Any suggestions please?

[Lucas_R]

Sounds like you might have a leaking injector or injector that is stuck open on cylinder 2.

The early EA888 engines are known for carbon buildup, and yes the carbon buildup can cause misifires but its usually on idle and low throttle inputs only. When they take the inlet manifold off to clean it, they may as well replace at least injector #2 while they are there as they will have perfect access to it.

[MIG]

One test you can do to see if there is a leaking injector is the high-pressure fuel measuring block. After shutting down the engine (at operating temp) you should see increased pressure due to the heat soaking; if the pressure keeps dropping you have a leak somewhere.

Has the simple test of swapping the coil packs been done?

[anotherdownunder]

Sounds like you might have a leaking injector or injector that is stuck open on cylinder 2.

Thanks, I was coming to think injector. Misfire only happens at low rpm and when run up to about 2k rpm seems to go. Never knew carbon only affected low rpm.

[anotherdownunder]

Thanks MIG, new coil pack and plugs fitted but old coil pack tested ok.

This helps your pressure suggestion check: Fuel Rail Pressure Test with VCDS by Ross-Tech - YouTube

[anotherdownunder]

Interesting. The misfire was transient and only on 2, so I suspected dodgy connector/wire/ECU as No 2 injector/coilpack/plug good. Next would have been compression check. The MFD has 'Factory Reset' (soft one?) but I removed the battery for an hour last night and on reconnection misfire went. After replacing data this morning went for an hour drive, lots turns/stops about 30 km and all good. Time will tell. Thanks for help, all.
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No fix. (Only seems to come back when wifey drives it. )
No 2 misfire at tickover; rev to 3 k; normal running; slight ''bump; irregular times; engine fault light goes out?

Got it booked into Wodonga Blacklocks - Skoda tomorrow (they bought the Skoda Franchise.)
Dreading it since when when I bought the Octavia 7 years ago I got Wodonga Skoda to find out why climatronic didn't work they wanted $800 to remove dash. I regassed, $64, and no problem. They also said ?224 thermistor, left footwell needed replacing. ($300) VCDS said no, working. I asked them to check timing chain tensioner. They said original, half-out but when I checked little round inspection plate the original sealant there + they left the intercooler pipe off!
What's left? Rings on 2; cracked piston; carbon only on 2?

Wodonga Skoda checked compression, all good. Said 4 new injectors needed (although misfire only on 2? and my measurement of rail pressure said no leaks but this is static, dynamic don't know.)
They are better since changing hands, they said they would quote or let me get injectors for them to fit or do it myself. Now to chase correct number.
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Saga continues. Skoda wanted $1600; $564 for injectors; 6 hours work. Had I agreed $1600 lost no fix?

Got a VW friend to check; random low compression cyl. 2; manifold off in 20 mins; cleaned all 4 injectors, new seals and swopped 1 & 2; decoked as it was bad. Misfire still on 2? Very random misfire; there on cold; not there when hot; stop for a short time it returns. Seems to be the inlet valve stems on 2 carboned up? Going to try some Rislone compression repair, if no go will have to pull head off to see, then things will escalate.

[anotherdownunder]

Started new thread hoping for new suggestions. 'ECU/loom Testing.'

[Lucas_R]

Have a look at the cam adjuster magnets which are bolted on to the upper timing chain cover. These can fail and cause misfires and rough idle.

[anotherdownunder]

Thanks Luca_R. Appears to be a 'gap' between cylinder wall and piston on cylinder 2. New engine I'm told.