[GasseousClay]

A few weeks ago, I posted here regarding a problem I have been having with my 2018 Elantra GT sport(1.6 turbo gdi engine) lately. I'm at 67k miles currently and have been getting a persistent check engine light - the code reads misfire in cylinder 3 every time. The dealer changed the spark plugs and then when the light came on again after a week later, went back to dealer...they said it's likely ignition coil problems. So, they replaced the ignition coil. The dreaded check engine light came on again a few days ago (again, code showing cylinder 3 misfires) and I am exasperated at this point(the dealership is about 2 hrs away...I live out in the countryside). Before I let this dealership milk all of my money and time, can anyone think of any other possible causes for this?

Also, at this point, does the 100k mile warranty apply?(have been paying out of pocket for everything so far).

I'm starting to despise...hate my car. :/

 

[mikl613]

Do you have a simple scan tool? Can try swapping the coils around and see if the misfire moves. If it doesn't could be a bad injector or compression issue.

If you paid a dealer out of pocket to fix the issue and it didn't work I would be taking it back to the dealer to warranty their work. Should be at least one year parts and labor covered. They could have dropped the spark plug when installing and screwed the gap.

 

[JP_N-Line]

I would start off with the basics, are the spark plugs still original? If so, at 67k miles they might need replaced. I would do this as preventative maintenance anyways.
Agreed with the above, try swapping around coils and see if it follows. Some people have had good luck with the MSD coil packs and they're relatively inexpensive.

If the above fails, it could be a case of carbon buildup but at 67k miles I wouldn't expect it to be all that bad.

Compression/ leak down check is never a bad idea since it's simple and gives the engine a general health statetement

 

[whitenite]

Interesting, cylinder 3 on my '19 Kia Cerato GT 1.6T (Forte GT) killed my HKS M45XS spark plug at 20k km. It started misfiring, and felt like running on 3 cyls, I took it out and cyl 3 spark plug was all sooty and smelled of fuel. I replaced with 4 orig factory sp plgs, and prob instantly disappeared. Re-inserted the suspect HKS plug, and immediately ran on 3 cyls again. Ordered a set of 4 factory plugs online for the time being.