Denso 4126 Spark Plug

Denso 4126 U-Groove Spark Plug Overview

Denso 4126 is a conventional spark plug from the U-Groove line, built for dependable ignition performance in secondary ignition systems. Its U-groove electrode design is engineered to improve ignitability, helping support smoother combustion and consistent engine efficiency in the right application.

For drivers searching for a Denso spark plug for Honda Civic, Toyota Corolla, or other import applications, this part number 4126 offers a straightforward OE-style replacement with the core materials and dimensions needed for proper fitment.

Key Features

• U-Groove design for improved ignitability
• 5000 ohm resistor for ignition noise suppression
• Copper center electrode core for stable heat transfer
• Nickel center and ground electrode tip materials
• Standard ground electrode and standard ground configuration
• Flat seat design
• 14.00 mm thread diameter, 19.00 mm reach, 16.0 mm hex size
• Pre-gapped to 0.8 mm
• Manufacturer heat range 24

Product Details

Denso U-Groove Conventional spark plugs are built around a practical ignition design that focuses on reliable spark delivery and efficient combustion. The U-shaped ground electrode helps expose the spark kernel more effectively than a standard flat edge, which can improve ignitability in engines that call for this style of plug. Part number 4126 uses a copper core center electrode, nickel tip materials, and a flat seat configuration to match the specifications required by many import engine applications.

This part cross-references DENSO Auto Parts U24ESR-N for the same application. When selecting a spark plug for Honda Civic or Toyota Corolla service, verify the thread diameter, reach, seat type, and heat range against the vehicle’s original specification before installation.

Common Issues This Spark Plug Can Address

• Hard starting caused by worn or fouled spark plugs
• Rough idle from inconsistent ignition performance
• Misfire conditions related to weak spark delivery
• Reduced fuel efficiency from degraded plug electrodes
• Engine hesitation during acceleration

Installation Notes

Confirm the correct spark plug gap, thread diameter, reach, seat type, and heat range before installation. Use proper spark plug service procedures, including checking the condition of ignition wires or coil-on-plug components, and torque the plug to the vehicle manufacturer’s specification. For fitment-based searches such as Denso 4126 spark plug for Honda Civic or Denso 4126 for Toyota Corolla, always match the engine application to the original equipment requirements.

Quality Assurance

Denso is known for OE-level ignition component engineering, and the U-Groove Conventional line is built to deliver consistent spark performance with application-specific dimensions and materials. Part number 4126 is manufactured to support reliable secondary ignition service when the vehicle calls for this plug specification.