Denso 4086 Spark Plug

Denso 4086 U-Groove Spark Plug Overview

The Denso 4086 spark plug is built for secondary ignition service with a U-Groove ground electrode design that promotes stronger ignitability and more consistent combustion. It is a practical OE-style choice for drivers searching for a Denso spark plug 4086 replacement for Honda Civic, Toyota Corolla, and other import applications that call for this specification.

Key Features

• U-Groove ground electrode tip design for improved spark exposure
• 5000 ohm resistor for radio noise suppression
• Copper center electrode core for efficient heat transfer
• Nickel center and ground electrode tip materials
• Standard ground configuration with one ground electrode
• Flat seat design
• 12.0 mm thread diameter, 19.0 mm reach, 18.0 mm hex size
• Manufacturer heat range 22 with 0.9 pre-gap size

Product Details

As part of Denso’s U-Groove Conventional line, the 4086 is engineered around a conventional spark plug layout with a specialized U-shaped ground electrode. That design increases the spark’s exposure area at the gap, helping support more reliable ignition and smoother engine operation in vehicles that specify this plug style. The copper-core construction helps manage heat, while the nickel electrode materials provide a durable firing surface for everyday service. This part cross-references DENSO Auto Parts (e.g., X22EPR-U9) for the same application.

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 performance
• Sluggish throttle response in aging ignition systems

Installation Notes and Tips

Verify thread diameter, reach, seat type, and heat range against the vehicle’s service specification before installation. For fitment-based searches, this Denso 4086 spark plug is commonly sought for Honda Civic and Toyota Corolla applications where the listed dimensions match the engine requirement. Check and set the gap to the specified 0.9 mm if adjustment is needed, and inspect ignition wires or coils during service to avoid repeat misfire concerns.

Quality Assurance

Denso’s U-Groove Conventional line focuses on OE-style ignition performance with a design intended to improve ignitability and engine efficiency through better spark exposure at the gap. The Denso 4086 is built to the listed electrical and dimensional specifications for accurate replacement selection.