Denso 3478 Spark Plug

Denso Iridium Long Life Spark Plug 3478

Denso 3478 is an Iridium Long Life spark plug built for OE-level ignition performance, durability, and emissions control. It is a direct-fit secondary ignition component for select Hyundai and Kia applications, including Hyundai Sonata, Tucson, and Santa Fe Sport, plus Kia Optima, Sorento, and Sportage.

The Iridium Long Life (SIP) line focuses on extended service life and stable spark delivery. This plug uses an iridium center electrode tip, a platinum needle ground electrode tip, and a 1.1 mm pre-gap for consistent ignition performance in modern engine designs.

Key Features

• Part number 3478 from Denso Iridium Long Life (SIP)
• Iridium center electrode tip with copper core
• Platinum needle ground electrode tip with nickel core
• Needle-to-needle ground configuration
• 5000 ohm resistance
• 1.1 mm pre-gap size
• Flat seat design
• 12.00 mm thread diameter and 26.50 mm reach
• Manufacturer heat range 16
• Direct replacement for select Hyundai and Kia engines

Product Details

Denso 3478 is engineered to meet strict OE performance, durability, and emissions standards. The iridium center electrode supports precise spark delivery, while the platinum needle ground design helps maintain consistent ignition characteristics over long service intervals. This spark plug is a strong match for drivers searching for a Denso 3478 spark plug for Hyundai Sonata 2011-2014, Kia Optima 2011-2016, or Kia Sorento 2012-2017 applications.

This part cross-references DENSO Auto Parts FXU16HR11 and Hyundai 18847-11160, 18851-11060 for the same application.

Vehicle Fitment

• Fits 2013-2017 Hyundai Santa Fe Sport, N/A
• Fits 2012-2017 Kia Sorento, N/A
• Fits 2011-2016 Kia Optima, N/A
• Fits 2014-2015 Hyundai Tucson, N/A
• Fits 2014-2015 Kia Sportage, N/A
• Fits 2011-2014 Hyundai Sonata, N/A

Common Issues This Part Addresses

• Misfire caused by worn spark plug electrodes
• Hard starting from weak ignition output
• Rough idle and inconsistent combustion
• Reduced fuel economy from degraded spark performance
• Emissions-related drivability concerns tied to ignition wear

Installation Notes and Tips

Verify engine application, thread diameter, reach, seat type, and heat range before installation. Use the specified gap setting for the engine and inspect ignition coils and boots during service. For Hyundai Sonata, Kia Optima, and Kia Sorento spark plug replacement, confirm the original part number and engine code against the vehicle catalog before installation.

Quality Assurance

Denso manufactures this spark plug to OE performance, durability, and emissions standards. The Iridium Long Life (SIP) design is intended for consistent ignition performance in the listed Hyundai and Kia applications.