Polo 6c GTI ongoing misfire issue (please help!)

[samhfisher1995]

1.8 TSI engine when I start it cold it always runs a tad rough like a slight misfire you can feel from the inside of the car. Sometimes it gets bad enough to trigger a flashing EML light and pops a code for random cylinder misfire. Always eases after 30 seconds/1 minute. Fine when driving/under load will rev all the way up to 6k no issue and still pulls fine so I have ruled out fuel pump/spark plugs/coil packs. The engine has just been rebuilt by a VW dealership (supposed to fix this issue) so I was thinking this would exclude any injector seals/gasket leaking? The rough/slight misfire happens only at idle, worst when cold. Still feels slightly jumpy when warmed up but it's so slight that anybody else jumping in the car wouldn't notice. If I drive the card hard for a few minutes so it gets red hot it idles butter smooth and the problem goes away. Anyone have any ideas?

Also this is my experience after getting my car serviced at my local dealership in regards to this issue.

So my problems started back in June 2019 when thankfully I was still under warranty. I had my water pump/thermostat housing replaced due to a slow leak that was traced to there. 4000 miles later coolant was still being lost so I returned to the dealership they looked into and replaced the same part again stating that it was definitely coming from there again. Guess what another 4000 miles later my coolant was low again and the third time they said they had replaced the thermostat housing. Fast forward until December, cold starts begin to get progressively rougher, but not because of ambient temperature sometimes fine when freezing. Eventually gets so rough a misfire flashing EML is triggered. I take it into the dealership I'm now a week out of factory warranty. They look at it and say it will be carbon build up on the intake valves so we'll clean it. I asked how could it be, I thought this engine had direct and port injection to prevent this problem he said he was just an advisor so didn't know. Went ahead with that they claimed to find carbon build up and gave me the keys. I went out to car park started it up and the car started like a bag of spanners and the dash lit up with EML and EPC lights now on. Obviously took it straight back in they said they would investigate further. They had the car for about 3 weeks and decided it was necessary to take the head off to inspect the engine after doing a compression test showing a leak between cylinder 3 and 4. They said the head gasket (necessary anyway) and the piston rings from these 2 had to be replaced due to damage. I had purchased an extended warranty due to my troubles earlier last year however, a warranty inspector came and decided that the claim would be rejected as he had diagnosed the cause of the problem (this was never explained to me before) as a failed spark plug. Apparently a piece of porcelain was missing from one that they pulled out and this had gone into the head. Because spark plugs are excluded from the warranty this would not be covered. Also that the ECU had recorded misfire prior to the start of my warranty so another reason why they didn't want to pay. So I ended up having to contribute £447 to this repair which I came to terms with at the time because I just wanted my car back and was happy to have it working again. I was given the keys and started the car, it didn't run great at all revs dancing around for the first 30 seconds and then settled I thought this was due to the engine just being rebuilt. Fast forward a few weeks and a couple of days ago I started the car cold, rough running until the EML started flashing again and then it evens out after 30 seconds or so. I have taken the car back again, now to see what they say this time. I really want to keep the car but not sure if it's a wise idea after all this, any advice on what I should do here?

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[Charl3210]

I have a similar misfire issue - can you let me know what the fix was?