Denso 4091 Spark Plug

Denso 4091 U-Groove Spark Plug Overview

The Denso 4091 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 efficient combustion in the right application. This spark plug is a practical choice for drivers searching for a Denso 4091 spark plug for Honda Civic, Toyota Corolla, or similar import applications that call for this specification.

Key Features

• U-Groove ground electrode tip design for improved spark exposure
• Nickel ground electrode tip material with a nickel center electrode tip
• Copper center electrode core for reliable heat transfer
• 5000 ohm resistor for ignition noise suppression
• Standard ground configuration with a single ground electrode
• Pre-gapped to 0.7 mm for the specified application
• Flat seat design, 12.00 mm thread diameter, 19.00 mm reach, and 18.0 mm hex size
• Manufacturer heat range 22

Product Details

As part of Denso’s U-Groove Conventional line, this spark plug focuses on dependable everyday operation rather than specialty racing use. The U-Groove electrode shape increases the exposed spark area, which can help the plug fire more consistently in engines that rely on precise ignition timing and stable combustion. The Denso 4091 is also referenced by DENSO Auto Parts part number X22ESR-U for the same application.

For buyers comparing ignition parts for Honda Civic, Toyota Corolla, and other import vehicles, the Denso 4091 offers a conventional design with OE-style dimensions and materials. Its copper core and nickel electrode construction are selected for balanced conductivity and durability in standard service intervals.

What This Spark Plug Helps Address

• Hard starting caused by worn or inefficient spark plugs
• Rough idle from inconsistent ignition firing
• Misfire conditions related to degraded secondary ignition components
• Reduced fuel efficiency from incomplete combustion
• Weak throttle response in engines needing fresh ignition service

Installation Notes and Tips

Verify thread diameter, reach, seat type, and heat range against the vehicle’s service specifications before installation. The pre-gap is set at 0.7 mm, but the final gap should always be checked against the engine requirement for the exact application. Use proper spark plug service procedures to avoid cross-threading the 12.00 mm threads and to ensure correct torque on the flat seat design.

For fitment-based searches, this part is commonly researched as a Denso 4091 spark plug for Honda Civic and Toyota Corolla ignition service. Confirm the engine’s required plug specification before ordering.

Quality Assurance

Denso manufactures ignition components to OE-level dimensional and material standards for conventional spark plug applications. The U-Groove Conventional design is engineered to support consistent ignitability and stable engine operation when installed in the correct vehicle application.