NGK 3690 Spark Plug

NGK Iridium IX Spark Plug TR7IX 3690

NGK Iridium IX Spark Plug 3690 is built for precise ignition performance in applications that call for a tapered-seat, 14 mm spark plug with a .708 reach and a .040 pre-gap. It uses an iridium center electrode tip, copper core center electrode, nickel ground electrode core, and a taper-cut ground design for consistent spark delivery.

Key Features

• NGK Iridium IX Spark Plug line for performance-focused ignition service
• Part number 3690, also identified as TR7IX
• Iridium center electrode tip material for stable spark characteristics
• Copper core center electrode for efficient heat transfer
• Nickel ground electrode core with standard ground configuration
• Taper-cut ground electrode tip design
• 5 k? resistance and non-removable nut terminal
• 14 mm thread diameter, 5/8 hex size, tapered seat, .708 reach
• Manufacturer heat range 7 with a .040 pre-gap

Product Details

This NGK Iridium IX Spark Plug is engineered for vehicles that require a tapered-seat plug with the listed dimensions and heat range. The Iridium IX product line focuses on durable electrode materials and stable ignition performance, while NGK’s long OE manufacturing background supports consistent fit and construction standards. This part number 3690 is a direct match for 2006-2009 Cadillac STS and 2006-2009 Cadillac XLR applications listed below.

This part cross-references DENSO Auto Parts 5327 for the same application.

What It Helps Address

• Misfire conditions caused by worn or fouled spark plugs
• Hard starting related to weak ignition output
• Rough idle from inconsistent spark delivery
• Reduced throttle response from degraded plug performance
• Maintenance replacement for Cadillac STS and Cadillac XLR ignition service

Installation Notes

• Fits 2006-2009 Cadillac STS, N/A
• Fits 2006-2009 Cadillac XLR, N/A
• Set spark plug gap to 0.040 inches before installation.
• Verify the tapered seat, 14 mm thread diameter, .708 reach, and heat range 7 match the engine specification.
• Use the correct torque procedure for the cylinder head material and plug seat style.

Quality Assurance

NGK is a major OE spark plug supplier with more than 80 years of automotive manufacturing experience and broad coverage across domestic and import vehicle applications. The brand’s North American and global production and distribution network supports consistent product availability and OE-level manufacturing standards.