Carbon cleaning done, still high rpm misfires... ideas?

[GroceryGTIer]

Plugs are new, oil is just changed, holds 20 psi to red line, but right at 5500 plus the car bucks and misfires, I don't really understand what else it could be.

Anyone had this? On UM k04 tune... I have not logged it, and have no way of doing so right now.

 

[Boscogn]

Does it misfire on a certain cylinder if so swap the coils around and see if it still misfires on same cylinder.

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[Boscogn]

Also anyway u can revert to stock tune and see if it still happens?

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[mk6'12gti]

Does it misfire on a certain cylinder if so swap the coils around and see if it still misfires on same cylinder.

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Assuming he has r8 coils since he is ko4 never really seen a r8 coil fail honestly. When the carbon cleaning was done did you take the manifold off. Chemicals or walnut blasting. Also were the injector seals replaced.

 

[snobrdrdan]

You said the plugs are new, but are they gapped properly & to what UM recommends?

 

[GroceryGTIer]

Ok, the plugs are gapped to .023, at the shop I had the UM tune done's recommendations, I've pulled the coils and they are likely not in the same order as before. I cannot go back to the stock tune from home... it's an hour and 45 minutes to the tuner. UM is a absolutely no real help, really it's the shop who takes care of their issues.
The k04 is ported and polished, the intercooler is a wagner, so a lot of added area there.... is it possible the car is running out of fuel that the tune is set for? I have a forge WGA, but I was having this issue before on the stock one too.

 

[thatspsychotic]

Plugs are new, oil is just changed, holds 20 psi to red line, but right at 5500 plus the car bucks and misfires, I don't really understand what else it could be.

Anyone had this? On UM k04 tune... I have not logged it, and have no way of doing so right now.

Has this always been present since you went K04 or did it develop more recently? When did it start? What are your other powertrain mods? No codes?

The specific RPM you mention sounds kinda like valve float actually. Without logging (or switching tunes to test if tune-related), it's pretty tough to tell for sure though. Perhaps the UM tune pushes the WGDC harder at high RPM, which might cause enough back pressure to float the valves.

This is a super common issue on Tiguans for K04 and up since they have weaker valve springs, but it's not unheard of on a GTI. Definitely not common at K04 but it is possible if you got unlucky with valve springs.

 

[GroceryGTIer]

Has this always been present since you went K04 or did it develop more recently? When did it start? What are your other powertrain mods? No codes?

The specific RPM you mention sounds kinda like valve float actually. Without logging (or switching tunes to test if tune-related), it's pretty tough to tell for sure though. Perhaps the UM tune pushes the WGDC harder at high RPM, which might cause enough back pressure to float the valves.

This is a super common issue on Tiguans for K04 and up since they have weaker valve springs, but it's not unheard of on a GTI. Definitely not common at K04 but it is possible if you got unlucky with valve springs.

I got the tune, it was ok for a while, started to notice it a few months later I guess it was. Checked for vacuum leaks, changed the plugs, regapped the plugs closer, still same issue. Thought for sure the carbon cleaning would help... nothing though. No codes except for a DV code because the turbosmart dead plug doesn't work. I guess I could try plugging the OEM DV in asn d just see how it acts.

I can get 12,5 on a trade, so I might just pick up a 2018... I'm tired of this car's issues.

 

[thatspsychotic]

I got the tune, it was ok for a while, started to notice it a few months later I guess it was. Checked for vacuum leaks, changed the plugs, regapped the plugs closer, still same issue. Thought for sure the carbon cleaning would help... nothing though. No codes except for a DV code because the turbosmart dead plug doesn't work. I guess I could try plugging the OEM DV in asn d just see how it acts.

I can get 12,5 on a trade, so I might just pick up a 2018... I'm tired of this car's issues.

Pretty sure this is valve springs. Based on APR's description of the issues, this can get worse over time as the valve springs age and lose some of their stiffness. More info: https://www.goapr.com/products/valve_springs.html

 

[Tony48]

Pretty sure this is valve springs. Based on APR's description of the issues, this can get worse over time as the valve springs age and lose some of their stiffness. More info: https://www.goapr.com/products/valve_springs.html

Directly from APR on that webpage. Sounds like you need to find a way to do a few logs OP. Unfortunately if this is the issue there is no fix short of replacing the valve springs. At least you will have the problem nailed down though (for your own sanity).

This issue accompanies misfires commonly above 5000 RPM. In some extreme cases, valves are forced open and the vehicle ceases accelerating any further. A quick datalog of intake mass airflow and boost pressure at wide open throttle will show a sudden rise in boost pressure with an immediate loss of airflow as pressure from the open valves is pushed back into the intake manifold.

 

[thatspsychotic]

I got the tune, it was ok for a while, started to notice it a few months later I guess it was. Checked for vacuum leaks, changed the plugs, regapped the plugs closer, still same issue. Thought for sure the carbon cleaning would help... nothing though. No codes except for a DV code because the turbosmart dead plug doesn't work. I guess I could try plugging the OEM DV in asn d just see how it acts.

I can get 12,5 on a trade, so I might just pick up a 2018... I'm tired of this car's issues.

Have you reached out to UM at all on this? I'd be shocked if they hadn't run across this same issue before. APR apparently offers a reduced power tune that seems to work with weak valve springs, UM may have something similar available. Crappy band aid, but not a lot of great options here.

 

[GroceryGTIer]

Have you reached out to UM at all on this? I'd be shocked if they hadn't run across this same issue before. APR apparently offers a reduced power tune that seems to work with weak valve springs, UM may have something similar available. Crappy band aid, but not a lot of great options here.

No, I'm just gonna trade the car. I'm tired of all this shit.... it's been enough headaches. It's either going to be a 2017 S Sport or a new 18 S in the white silver metallic.

 

[jerichogabe25]

Plugs are new, oil is just changed, holds 20 psi to red line, but right at 5500 plus the car bucks and misfires, I don't really understand what else it could be.

Anyone had this? On UM k04 tune... I have not logged it, and have no way of doing so right now.

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[thatspsychotic]

No, I'm just gonna trade the car. I'm tired of all this shit.... it's been enough headaches. It's either going to be a 2017 S Sport or a new 18 S in the white silver metallic.

That's fair. $12,500 is a good trade in value, my car has far too many miles to be worth much on a trade in. Mk7s are awesome and I think more of a pain to work on but there are probably fewer problems lurking after what they learned from Mk6.

Makes me confident in not wanting to go K04, because I kinda don't want to know if my valve springs are weak lol.

I assume you'll part out your Mk6?

 

[GroceryGTIer]

That's fair. $12,500 is a good trade in value, my car has far too many miles to be worth much on a trade in. Mk7s are awesome and I think more of a pain to work on but there are probably fewer problems lurking after what they learned from Mk6.

Makes me confident in not wanting to go K04, because I kinda don't want to know if my valve springs are weak lol.

I assume you'll part out your Mk6?

I don't think I'll part out much no, I'm sick of working on the car. The DP, intake, and CC I may sell, but I'm not digging into the front to get the IC, or taking the turbo off for a 3rd time... no way. A shame because that turbo is p&p with a forge WG on it. Motor mounts, etc.