Ignition Coil and Iridium Spark Plugs for Audi S4 (2005-2009) 4.2L

Direct-Replacement Ignition Coil and Iridium Spark Plug Kit for 2005-2009 Audi S4

What it Does: The ignition coil and iridium spark plug kit replaces degraded factory ignition components on the 2005-2009 Audi S4 to eliminate cylinder misfires, smooth idle harmonics, and restore peak combustion efficiency.

The Stock Audi S4 Thermal Ignition Breakdown

The 40-valve BHF 4.2L V8 operates with an 11.0:1 static compression ratio packed tightly within the compact B7 chassis engine bay. Due to restricted airflow around the aluminum cylinder heads, factory pencil coils endure continuous thermal soak. Over time, heat cycles cause the OEM potting epoxy to crystallize and micro-crack, breaking down dielectric insulation across the secondary copper windings. Concurrently, factory spark plug electrodes erode, raising gap resistance. This voltage spike forces electrical discharge to ground through fractured silicone boots, precipitating P0300–P0308 misfires, poor catalyst performance, and unburned fuel contamination.

The Engineering Solution

This ignition kit pairs eight direct-fit coil-on-plug units with matched fine-wire iridium spark plugs designed for high thermal endurance. Each coil pack features vacuum-impregnated high-grade copper windings and thermoset epoxy potting to resist internal flashover and withstand severe underhood temperatures. Heavy-duty fluorosilicone boots prevent corona discharge and track-arcing down the plug well. The matched iridium plugs feature laser-welded 0.6mm center electrodes, dramatically reducing primary strike voltage demands, preventing spark blow-out at 7,000 RPM, and sustaining continuous flame kernel propagation.

Technical Specifications

Compatibility

• 2005 Audi S4 Base Sedan / Avant / Cabriolet 4.2L V8
• 2006 Audi S4 Base Sedan / Avant / Cabriolet 4.2L V8
• 2007 Audi S4 Base Sedan / Avant / Cabriolet 4.2L V8
• 2008 Audi S4 Base Sedan / Avant / Cabriolet 4.2L V8
• 2009 Audi S4 Cabriolet 4.2L V8

Frequently Asked Questions

Does this fit the B7 S4?
Yes, this is a direct fit for the 2005-2009 Audi S4 equipped with the 4.2L V8 BHF engine.

Do these iridium spark plugs require manual gapping before installation?
No, these plugs come pre-gapped to factory specifications; altering the fine iridium center wire manually can damage the brittle electrode coating.

The Audi Precision Standard

Calibrated specifically to OEM secondary resistance standards, this ignition package works seamlessly with the factory Bosch Motronic ECU without triggering false diagnostic knock codes, erratic cold starts, or unwanted check engine lights.