Denso 4009 Spark Plug

Denso 4009 U-Groove Spark Plug

Denso 4009 is a conventional spark plug built for steady ignition performance in secondary ignition systems. Its U-Groove ground electrode design helps improve ignitability, supporting more complete combustion and consistent engine efficiency.

Key Features

• U-Groove ground electrode tip design for improved spark exposure
• Nickel ground electrode tip material with a copper core center electrode
• Standard ground configuration with a flat seat
• Pre-gapped to 0.7 for direct service use
• 14.00 mm thread diameter and 12.70 mm reach
• 16.0 mm hex size for proper socket fitment
• Manufacturer heat range 24

Product Details

This Denso spark plug is part of the U-Groove Conventional line, a product family focused on dependable ignition characteristics in everyday driving conditions. The U-shaped ground electrode helps expose the spark kernel more effectively, while the copper core center electrode supports efficient heat transfer. For drivers searching for a Denso 4009 spark plug, Denso 4009 ignition service part, or a U-Groove conventional spark plug for secondary ignition maintenance, this part is built around those core service needs. This part cross-references DENSO Auto Parts (e.g., U24FS-U) for the same application.

What It Helps Address

• Hard starting caused by worn or inconsistent spark plugs
• Rough idle from weak ignition output
• Misfire symptoms related to degraded plug electrodes
• Reduced combustion efficiency from excessive electrode wear
• Service intervals where a conventional replacement plug is required

Installation Notes and Tips

Verify thread diameter, reach, seat type, and heat range before installation. The pre-gap size is 0.7, but final gap verification is still recommended during service. Use the correct 16.0 mm spark plug socket and follow the vehicle manufacturer’s torque specification to avoid thread or seat damage. For vehicle-specific searches, this part is commonly researched as a Denso 4009 spark plug for Honda Civic and Denso 4009 spark plug for Toyota Corolla applications, so confirm the exact engine and plug specification before ordering.

Quality Assurance

Denso is an established ignition component manufacturer, and the U-Groove Conventional line is engineered around practical OE-style service requirements. Part number 4009 is built to the listed specifications for accurate replacement selection.