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2021 i30 N-Line -Rough Idle, Choking upon cold start, Black smoke fluttering out

NON092 · 6 · 8760

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Offline NON092

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    • au Australia
      Australia, Brisbane
Hey All,

Recently purchased an ex demo 2021 I30 N-Line (140kms on the clock) from a local Hyundai Dealership in Brisbane.
When first purchased it started fine and with no issues.
Now fast forward to now with around 3,500kms on the clock i'm having some real issues with the cold starting of the car.
- Rough idle
- Choking almost similar to when you start a lawn mower
- Black flutters of smoke popping out upon each choke.

Now from my personal experience, i've never had a car do this at all, especially a brand new car with such little kms on the clock.

The technician at the dealership stated that this is a normal sound and that there's no issues at all. "That's just how it is". Which concerns me. While it seems to even out after 2 to 3 minutes, i still believe a brand new car should start with ease.

What i'm seeing online is something to do with factory coils/plugs being blocked up causing this. other things i've seen is an ecu update due to incorrect readings of air-fuel ratio etc upon start up.

Just curious to know if this is just me or whether this is an issue that's more commonly wide spread.
Any help or advice would be greatly appreciated.

  • 2021, PD, 5 Door Hatch, Petrol 1.6LT, Manual, White

Offline Lorian

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    • gb United Kingdom

  • Midlands, UK N-Line T-GDi

Offline seanharry

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    • au Australia
Hey Dean,

I am having exactly the same problem. I have video proof of this as well that shows the rough idle and smoke.

It did this the next day after I purchased it new. It only has 1000kms on the clock.

I took the car back to the dealer and they said this is normal and later told me that they have had a few of these cars do the same thing and they haven’t found a fix. I returned the car again and they back flipped and said it is normal again.

I am beyond frustrated.

When I try to drive the car when it is doing this it hesitates and almost stalls. Also when I am driving up a hill it feels like it is stuttering.

I had a coil pack go in another car I used to own and it feels similar.

I have escalated it with Hyundai and I am waiting on their response.

So disappointed 😔
  • I30 N Line

Offline rein

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    • au Australia
      Australia, Sydney
Hey Dean & Sean,

I have a 2019 N-Line and experienced similar issues (except for black smoke). Not sure if 2021 is the updated Smart Stream engine though.

From experience and reading forums, fixes for these issues could be:
  • Replace Spark plugs
  • Replace ignition coils
  • Walnut blast to remove carbon build up
  • Chemical carbon flush
  • Replace Fuel injectors

In my case, I think there were issues with the cylinder/compression/scouring inside. I've been talking to Hyundai for a handful of months, and I am having a full engine rebuild which has taken them over 3 1/2 months. Hope both of yours is an easy fix.

Same with both of you, I am extremely disappointed and it was full effort to get it covered under warranty.
  • i30 N-Line MT 2019

Offline Nline

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    • au Australia
Hi, just wondering if anyone had found any resolution to this issue?
  • 2022 PD4 5 Door Hatch, N-Line Petrol 1.6lt, Auto

Offline FDGazza

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    • au Australia
Hi Dean Sean and Rein,

The cold start " choking " that you are experiencing is not normal at all period.
Black smoke indicates excess fuel caused by either to much fuel being sheduled by the ECU ( faulty input signals or sensors ) or the correct amount of fuel is going in but is not ignited due faulty plugs or coils.
Have you seen any changes in starting with the recent cold mornings in Brisbane Dean ?
Are hot starts normal ?
When the Dealer looked at the car , did it return any fault codes ?
I've had a 2017 I30 SR with 45000kms , it has the same 1.6 turbo engine , used in club level motor sport , never had any thing like you are experiencing .
  • 2021 I30N PDe 5 Door Hatch, Petrol 2.0lt,Turbo 8 speed DCT, White

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