Denso 4004 Spark Plug

Denso 4004 U-Groove Spark Plug

The Denso 4004 is a conventional spark plug built around a U-groove ground electrode design for improved ignitability and more consistent combustion. It uses a copper core center electrode with nickel tip materials and a 5,000-ohm resistor for stable secondary ignition performance.

For drivers searching for a Denso spark plug 4004 replacement, this U-Groove Conventional plug is a direct choice for ignition service where OE-style dimensions matter. It is also a practical option for Honda Civic spark plug replacement searches and other vehicle-specific ignition maintenance needs.

Key Features

• U-groove ground electrode design for improved spark exposure
• Conventional spark plug construction for everyday ignition service
• Copper core center electrode for efficient heat transfer
• Nickel center and ground electrode tip materials
• 5,000-ohm resistor for reduced electrical noise
• 14.00 mm thread diameter, 12.70 mm reach, and flat seat design
• 0.7 pre-gap size with a standard ground configuration
• 16.0 mm hex size for proper socket fitment

Product Details

Denso’s U-Groove Conventional line focuses on reliable spark delivery through a ground electrode shape that helps expose the flame kernel more effectively than a standard flat design. The Denso 4004 follows OE-style spark plug dimensions and materials, making it a straightforward service part for ignition tune-ups where consistent firing and stable engine operation are priorities. The copper core and nickel electrode construction support dependable heat control and long-term secondary ignition performance.

This part cross-references DENSO Auto Parts U20FSR-U for the same application. For shoppers comparing Denso 4004, U20FSR-U, and other ignition service parts, this spark plug is built to match the specified thread, reach, seat, and gap requirements.

What It Helps Address

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

Installation Notes and Tips

Verify thread diameter, reach, seat type, and pre-gap before installation. Use the correct 16.0 mm spark plug socket and follow the vehicle manufacturer’s torque specification. Inspect ignition wires or coil-on-plug components during service, and confirm the plug gap matches the engine requirement before final tightening. For Honda Civic spark plug service and other vehicle-specific applications, always confirm the exact engine fitment before ordering.

Quality Assurance

Denso manufactures ignition components to OE-style specifications, and the 4004 spark plug is built with defined electrical resistance, electrode materials, and dimensional accuracy for consistent service replacement.