Early Hyundai, Kia, and Genesis GDI engines (2011–2016) suffered from carbon buildup on intake valves due to portless GDI design. Issues included misfires, rough idle, loss of power, and the need for periodic walnut blasting or induction cleaning. Class actions and recalls have referenced these defects, with remedies including extended warranties and service campaigns.
| Year(s) | Make | Model | Should Purchase? | Notes | |
|---|---|---|---|---|---|
| 2011 2012 2013 2014 2015 2016 | Hyundai | Sonata | Caution |
Engine: Theta II 2.4L GDI – G4KE Transmission: 6AT – A6MF2 Intake valve deposits → misfires, rough idle, loss of power Class action filings reference carbon buildup defects |
|
| 2011 2012 2013 2014 2015 2016 | Kia | Optima | Caution |
Engine: Theta II 2.4L GDI – G4KE Transmission: 6AT – A6MF2 Carbon buildup on intake valves; periodic walnut blasting required Covered in settlement expansions and service bulletins |
|
| 2013 2014 2015 2016 | Hyundai | Elantra | Caution |
Engine: Nu 2.0L GDI – G4NA Transmission: 6AT – A6MF1 Intake valve deposits → misfires, rough idle Legal context: referenced in consumer complaints and TSBs |
|
| 2014 2015 2016 | Kia | Forte | Caution |
Engine: Nu 2.0L GDI – G4NA Transmission: 6AT – A6MF1 Carbon buildup → misfires, reduced performance Covered by service campaigns; class action references noted |
|
| 2012 2013 2014 2015 2016 | Hyundai | Veloster Turbo | Caution |
Engine: Gamma 1.6L Turbo GDI – G4FJ Transmission: 6MT – M6GF2 / 6AT – A6MF1 Intake valve deposits → misfires, rough idle, loss of power Remedy: periodic induction cleaning; legal filings reference defect |
|
| 2012 2013 2014 2015 2016 | Kia | Rio | Caution |
Engine: Gamma 1.6L GDI – G4FD Transmission: 6MT – M6GF2 / 6AT – A6MF1 Carbon buildup → misfires, rough idle Covered by service bulletins; class action references noted |
|
| 2012 2013 2014 2015 2016 | Hyundai | Accent | Caution |
Engine: Gamma 1.6L GDI – G4FD Transmission: 6MT – M6GF2 / 6AT – A6MF1 Intake valve deposits → misfires, rough idle Remedy: periodic walnut blasting; legal filings reference defect |