Ignition coil and spark plug replacement on a 2008–2012 Audi S5 Coupe with the 4.2L V8 can address a confirmed ignition misfire that causes rough idle, hesitation or reduced power. P0300 indicates random or multiple-cylinder misfire; P0301 through P0308 identify misfires assigned to individual cylinders. These codes describe what the engine computer detected, not which component has failed. Check the plug, coil, connector and other possible causes before ordering a kit.
This guide focuses on the naturally aspirated 4.2L CAUA V8 coupe. The S5 name also appears on cars with a supercharged 3.0L V6, including the cabriolet; their access procedures and parts requirements differ. The featured package services four cylinders. A full eight-cylinder coil-and-plug replacement requires eight of each component, so establish the actual repair scope before comparing prices.
Intermediate; confined access on both banks
About 2–4 hours for a prepared DIYer; diagnosis and damaged connectors add time
About $140–$220 for two aftermarket four-cylinder kits, before tax; planning estimate
Featured replacement kit
The featured item is the A-Premium APIC0568 red ignition coil and iridium spark plug kit, ASIN B09Z6JY95Q. It contains four coils and four plugs, rather than eight coils. The manufacturer’s kit catalog lists the 2008–2012 S5, and the exact Amazon fitment bullet specifies the 4.2L V8. Coil interchange references include UF529 and 06E905115-series numbers. An interchange number helps identify a component family but does not establish the correct spark plug for every car using that coil. Confirm both components against the engine code and the supplied plug markings.
View the exact coil and spark plug kit
Vehicle compatibility and quantity
| Application | Engine and restrictions | Coverage and purchasing check |
|---|---|---|
| 2008–2012 Audi S5 Coupe | 4.2L naturally aspirated V8; CAUA application | Primary repair scope. Eight cylinders; two of the featured four-coil/four-plug packages for a complete set. |
| 2007–2011 Audi A6 Quattro; 2007–2012 Audi A8 Quattro | 4.2L V8 | Additional seller-listed applications; their engine-bay access is outside this S5 procedure. |
| 2007–2010 Audi Q7; 2008–2012 and 2014–2015 Audi R8 | 4.2L gasoline V8 | Additional listing coverage. R8 years are discontinuous; do not fill the 2013 gap. |
| 2007–2009 and 2011–2015 Volkswagen Touareg | 4.2L V8; verify market and actual engine | Catalog coverage does not mean this engine was offered in every country or every trim. |
| S5 3.0L V6; Porsche Cayenne/Panamera | Different applications from the S5 4.2L scope | Broad product-title and coil-only references are insufficient to extend the complete kit or this procedure. |
Read the selected kit’s compatibility details, not just the long marketplace title. Compare connector shape, four-pin arrangement, boot length and plug thread/seat design before opening packaging. The current manufacturer page states a 0.028–0.032-inch plug gap range. That is a product specification, not permission to apply it to every engine in a broad coil interchange list. Obtain the plug manufacturer’s application-specific installation instructions and do not force a fine-wire electrode to an assumed gap.
Symptoms and diagnosis before buying parts
- Record every stored and pending code and the conditions in the freeze frame. A cold-start-only misfire, a misfire under load and a persistent single-cylinder miss can have different causes. Save the information before clearing anything.
- Check the intake connections and coil harness for loose plugs, damaged locks, pin corrosion or chafed wires. Photograph the connector routing. Pulling on wires can create a second fault while investigating the first.
- Look down each accessible plug well for oil, water, cracked boots and carbon tracking. Fluid contamination needs its own repair; a new coil installed into a contaminated well can fail again.
- If a single cylinder is implicated and the coils are identical, moving the suspect coil to another cylinder can help isolate it. Work with the ignition off, label both positions and recheck the misfire afterward. A misfire that follows the coil supports a coil fault; one that stays needs further testing.
- Inspect removed plugs individually and keep them labeled by cylinder. A cracked insulator, badly worn electrode or unusual deposits can guide diagnosis, but deposits alone are not a complete fuel, compression or oil-consumption test.
- Consider injector performance, intake leaks, compression and other mechanical conditions when ignition checks do not explain the complaint. Do not replace eight coils simply because a scanner displays a cylinder number.
Tools and supplies
Choose tools for the actual fastener and plug dimensions on the vehicle. The linked general-purpose products are exact listings; the special puller and configuration-dependent items remain specified below so they are not overlooked.
| Tool or Supply | Exact Product | Product Link | Purpose and Selection Check |
|---|---|---|---|
| OBD-II code reader | Autel AutoLink AL319 | View exact product | Read stored/pending engine codes and freeze-frame data before disconnecting the battery. A basic reader does not replace manufacturer-level diagnosis. |
| 3/8-inch ratchet, sockets and extensions | TEKTON SKT15301, 46-piece set; metric sizes 8–19 mm | View exact product | Metric sockets, ratchet and extensions for matching access hardware. This 8–19 mm set is not a Torx-bit set. |
| Spark-plug socket | GEARWRENCH 80546, 3/8-inch-drive 5/8-inch magnetic swivel socket, 6-inch length | View exact product | 5/8-inch (approximately 16 mm) plug socket for the matching hex. Confirm the supplied plug hex and tube clearance; do not scrape the thin-walled plug tubes. |
| Spark-plug torque wrench | TEKTON TRQ51402, 3/8-inch drive, 10–100 ft-lb | View exact product | The 10–100 ft-lb range covers the factory 30 N·m (about 22 ft-lb) plug reference. Use only after the exact replacement plug’s installation specification is established. |
| Eye protection | DEWALT DPG82-11 Concealer, clear lens, one pair | View exact product | Eye protection for cleaning wells and handling brittle plastic or debris. |
| Ignition coil puller | Audi/VW T40039 or a correctly shaped equivalent | Select to the specification at right | Required for the CAUA coil design. Confirm the tool engages the coil body securely; do not lever against plastic housings or pull the wires. |
| Access fastener bits and low-range torque tool | Bits matching the airbox, harness brackets and reservoir fasteners | Select to the specification at right | Inspect the installed hardware first. Obtain each fastener’s service torque; the 30 N·m plug specification is not a universal access-bolt setting. |
| Debris removal and labeling | Vacuum with narrow nozzle, clean cloths, labels and work light | Select to the specification at right | Clean around the closed plug wells before loosening a plug. Use gentle suction rather than driving grit into an open cylinder. |
| Plug gap gauge | Wire-type gauge suitable for the exact plug specification | Select to the specification at right | Measure without levering against the fine center electrode. Replace a damaged or incorrect plug rather than forcing it to fit. |
DIY versus professional cost
These are planning estimates in U.S. dollars, not live marketplace prices or a repair-shop quote. The calculation assumes a complete eight-coil/eight-plug service with no broken connectors, thread repairs, oil leaks or additional diagnosis.
| Expense | Planning estimate | Assumptions |
|---|---|---|
| Replacement parts | $140–$220 | Two four-coil/four-plug aftermarket kits; confirm contents and price at checkout. |
| Consumables | $10–$25 | Cleaning and labeling supplies; excludes repairing oil or coolant leaks. |
| Tools if not already owned | $100–$250 | Borrowing an appropriate torque wrench, puller and sockets can reduce this. |
| DIY total, tools already owned | $150–$245 | Parts plus basic consumables; your labor is not priced. |
| DIY total, buying tools | $250–$495 | Adds the estimated tool allowance. |
| Shop parts and labor | $400–$1,100 | Illustrative $200–$500 parts allowance plus 2–3 hours at $100–$200/hour; tax and diagnosis extra. |
Ask whether a shop quote covers one failed coil, all eight coils, scheduled plugs, or a combination. Dealer-supplied parts may cost more than the featured aftermarket kit. Comparing a four-cylinder package price with an eight-cylinder installed service can make the apparent savings misleading.
Step-by-step replacement overview
- Confirm the repair and parts. Verify the VIN, engine code and 4.2L coupe configuration. Count the replacement components and check each coil and plug against the removed part and application catalog. Resolve plug heat range, reach, seat, gap and installation instructions before installation. Set aside any damaged or mismatched item.
- Prepare the work area. Allow the engine to become cold, save diagnostic information and switch the ignition off. Remove loose items from the engine bay and arrange a labeled tray for each bank. Follow the vehicle’s electrical isolation procedure where required; consider settings that may need resetting after a battery disconnect.
- Open access to the first bank. On the CAUA service procedure, bank 1 access involves the lower air-filter housing. Photograph the air duct and connector arrangement before moving it. Release clips and clamps with the correct tool, keep dirt out of the intake opening and avoid straining attached ventilation lines.
- Create clearance on the other bank. The CAUA procedure moves the coolant expansion tank aside after releasing its mounting and bottom level-sensor connection. Keep its coolant hoses attached and support the tank without twisting the hoses. Do not hang it from a hose or disconnect hot coolant plumbing.
- Release the coil harness. Free the relevant harness retaining bolts and clips. Use the T40039-type puller to raise the coils approximately 30 mm, then release their electrical connectors together as directed by the factory procedure. Do not yank a coil against a still-connected rigid harness. Keep the connectors clean and dry.
- Remove coils and clean the wells. Extract each coil squarely and label its cylinder. Inspect the boot for tears and tracking. Vacuum loose debris before removing any spark plug, and address liquid contamination first. Do not allow grit, loose rubber or broken porcelain to enter the cylinder.
- Remove and compare the plugs. Seat the correct spark-plug socket fully and keep the extension aligned with the plug. Loosen gently by hand; stop if resistance suggests seized threads or damage. Compare the old and new thread reach, seat and terminal arrangement. Use a cylinder-labeled tray so an unusual plug can be traced back during diagnosis.
- Install plugs with the correct specification. Start each plug by hand with the extension, without the ratchet, and confirm it turns freely into its seat. The Audi CAUA ignition overview specifies 30 N·m, approximately 22 ft-lb, for its specified spark plug. Apply that factory reference only to a confirmed suitable plug installation; reconcile any different replacement-plug instruction before proceeding. Do not add anti-seize or other thread lubricant unless the exact plug maker requires it.
- Seat coils and reconnect the harness. Ensure the plug terminal and coil boot are compatible, then press each coil straight into place. Engage every connector lock and restore the original routing so wires are not stretched across hot or moving parts. Tighten access and harness fasteners to their own specifications, never to the spark-plug torque.
- Restore intake and reservoir components. Refit the airbox and ducts with their seals properly positioned. Reconnect the mass-airflow and coolant-level connections that were disturbed, secure the reservoir and check hose routing. Account for every tool and cloth before starting the engine.
- Check the result. Start the engine and watch for rough running, warning messages or abnormal sounds. Stop promptly if a severe misfire appears. Recheck connectors and intake seals before condemning another component. Once it runs normally, make a short controlled road test and scan again for pending codes. Keep the original codes and repair record; clearing codes alone is not proof of a successful repair.
Common mistakes to avoid
- Ordering one four-coil kit for an eight-cylinder complete replacement or assuming an eight-piece description means eight coils.
- Using a 3.0L S5 cabriolet tutorial as a direct guide for the 4.2L coupe, or treating every model named in the listing title as complete-kit coverage.
- Disconnecting coolant hoses unnecessarily or letting the expansion tank hang unsupported.
- Pulling coils by their harness, forcing damaged connector locks or reinstalling oil-soaked boots without repairing the source.
- Installing plugs with an impact tool, applying the plug torque to small access bolts, or ignoring a mismatch between the actual plug and its installation instructions.
- Calling the repair successful after erasing codes without checking idle quality, load response and pending faults.
Frequently asked questions
Does one featured kit cover the whole V8?
No. It contains four coils and four plugs. A full eight-cylinder replacement needs eight of each. If diagnosis calls for fewer parts, buy for that scope rather than automatically replacing working components.
Will this guide work for the S5 convertible?
The scope is the 2008–2012 S5 Coupe 4.2L CAUA V8. The 3.0L supercharged V6 has different packaging and parts requirements. Identify the engine rather than relying on the S5 badge.
Can I replace only the failed coil?
Yes, when diagnosis isolates it and the remaining coils and plugs are serviceable. If plugs are due by the maintenance schedule, plan their replacement separately; one coil failure does not prove every coil is defective.
Can I use the listing’s gap figure as the vehicle specification?
No. Check the exact plug and engine application. The product maker’s listed range and the engine’s requirement must agree; do not interpret a mislabeled unit or bend a fine-wire electrode to make an uncertain plug fit.
Why does the same cylinder still misfire after replacement?
Possible causes include a connector problem, damaged new part, fluid in the well, injector trouble, an intake leak or a mechanical fault. Recheck the work and diagnostic evidence before purchasing another set.
Are the photograph and pictured plugs the exact kit?
No. The photograph illustrates used spark plugs as a component reference. It does not show the supplied kit, establish its condition or demonstrate this engine’s access layout.
Sources and further reading
- Exact featured product listing — A-Premium APIC0568
- A-Premium APIC0568 specifications and kit compatibility
- Audi CAUA ignition assembly overview — reproduced factory service information
- Audi factory CAUA S5 coil-removal notes (cross-linked manual page identifies 2008–2012 S5)
- Reference photograph, creator and reuse license