Ignition Coil Guide for the 2004-2009 Audi S4 (B6/B7)
Solve misfires and restore your S4's 4.2L V8 power by choosing the right ignition coils.
- Ignition coil failure is a common issue for the 2004-2009 S4, causing misfires and a flashing check engine light.
- It is highly recommended to replace all eight coils at once using a quality brand like Bosch, NGK, or Delphi.
- A flashing check engine light means you should stop driving to prevent expensive damage to your catalytic converters.
- This is an easy DIY repair that most owners can complete in under an hour with basic tools.
Is Your S4's V8 Running Rough? It Could Be the Ignition Coils.
Ignition coil failure is a well-known issue on this generation of Audi S4. The coils are exposed to significant heat from the 4.2L V8 engine, which can cause them to wear out over time. Moisture getting into the engine bay, sometimes from washing the engine, can also cause them to fail. When a coil fails, the spark plug for that cylinder can't fire, leading to an engine misfire.
Flashing Check Engine Light: Pull Over!
If your check engine light is flashing, it signals a severe misfire. Unburned fuel is being sent into the exhaust, which can quickly damage your expensive catalytic converters. It is strongly recommended to stop driving the vehicle to prevent further damage.
Symptoms of a Failing Ignition Coil
A bad ignition coil will cause noticeable problems with how your engine runs. Common signs include:
🎬 See a visual guide on the most common bad coil symptoms.- Engine Misfires: The engine may sputter, hesitate, or jerk during acceleration.
- Rough Idle: Your car may shake or vibrate more than usual when stopped.
- Check Engine Light: A solid or flashing check engine light is common. You will likely see codes like P0300 (random/multiple misfires) or P0301-P0308 for specific cylinders.
- Loss of Power: Your S4 will feel noticeably sluggish and slow to accelerate.
- Reduced Fuel Economy: The engine runs inefficiently during a misfire, causing it to use more fuel.
Choosing the Right Aftermarket Ignition Coils
When replacing ignition coils, you have several options. While you can replace just the one failed coil, it is highly recommended to replace all eight at the same time. The other original coils are likely near the end of their service life and will probably fail soon after. For the 2004-2009 S4, aftermarket quality varies, so it's best to stick with proven brands.
Brand Quality Tiers
- Premium (OEM-Equivalent): Brands like Bosch, NGK, and Delphi are often original equipment suppliers to Audi or produce parts that meet or exceed OEM standards. Bosch is a very common OEM brand for this vehicle. These offer the best reliability and performance, making them a safe bet for your S4.
- Quality Aftermarket: Brands such as Hitachi, Spectra, and Standard Ignition (SMP) generally provide good quality and performance for daily driving. They are a solid choice if you're looking for a balance between cost and reliability.
- Economy: Lower-cost brands may be available, but their long-term durability can be questionable. Given the performance nature of the S4 and the history of coil failures, investing in a higher-quality brand is a wise decision to avoid future headaches.
| Part Type | Estimated Cost (Set of 8) |
|---|---|
| New OEM | $400 - $800+ |
| New Aftermarket (Premium) | $300 - $600 |
| New Aftermarket (Economy) | $180 - $250 |
| Shop Labor | $85 - $125 |
Pro Tip: Check for Oil Leaks
When you remove the old ignition coils, inspect the spark plug tubes for any signs of oil. Oil in this area indicates a leaking valve cover gasket. This leak should be repaired before installing new coils, as the oil can cause the new parts to fail prematurely.
Frequently Asked Questions (FAQ)
Do I have to replace all 8 ignition coils at once?
It is strongly recommended. The ignition coils on your S4 are all the same age and have been exposed to the same conditions. If one has failed, the others are likely not far behind. Replacing them all at once is preventative maintenance that saves you from repeated repairs.
Is this a difficult DIY job?
No, this is a very straightforward job for a DIY mechanic. 🎬 Watch this step-by-step walkthrough for replacing your S4's ignition coils. The coils are easily accessible on top of the engine. The replacement involves removing a few covers, disconnecting the electrical connectors, and pulling the old coils out. No special tools are required, though a tool to help pull the coils can make it easier.
How do I find which ignition coil is bad?
If you have a check engine light, an OBD2 scanner will give you a trouble code. Codes P0301 through P0308 point to a misfire in a specific cylinder (e.g., P0306 is cylinder 6). If you get a P0300 code for random misfires, you can swap a coil from a misfiring cylinder with one from a known good cylinder. If the misfire code follows the coil to the new cylinder, you've found the bad coil.
🎬 Watch a real-world diagnosis of an Audi S4 engine misfire.Are there any recalls for the ignition coils on my S4?
Searches for recalls on the NHTSA website did not show any specific safety recalls for ignition coil failure for the 2004-2009 S4. However, a Technical Service Bulletin (TSB) was issued in 2007 (TSB #2013623/3) for misfires caused by moisture getting into the ignition coils on certain 2005-2007 S4 models, indicating it was a recognized problem.
Helpful Videos
Technical Specifications
OEM Part Numbers: 077905115T 077905115F 077905115H 077905115Q
This vehicle uses a coil-on-plug system with 8 individual ignition coils.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Audi S4:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your S4's V8 Running Rough? It Could Be the Ignition Coils.
- Flashing Check Engine Light: Pull Over!
- Symptoms of a Failing Ignition Coil
- Choosing the Right Aftermarket Ignition Coils
- Brand Quality Tiers
- Pro Tip: Check for Oil Leaks
- Frequently Asked Questions (FAQ)
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