Audi A4 Spark Plugs: Intervals, Fitment & Warning Signs
A genuinely honest account: a coil pack replacement didn't fix a misfire, which was actually traced to carbon buildup on the plugs themselves, even on a car just three years old — plus a money-saving diagnostic technique to test a coil before buying a replacement.
Illustration for editorial purposes
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OEM Part Number: confirm via engine code — aftermarket NGK 1675 / Bosch 0 241 245 673
| Petrol engines in this generation | B8: 1.8 TFSI 120, 160 and 170 HP (also quattro); 2.0 TFSI 180, 211, 220 and 224 HP (also quattro and Flexfuel); 3.0 TFSI quattro 272 HP; 3.2 FSI 265 HP; S4 quattro 333 HP. B9: 1.4 TFSI 150 HP; 2.0 TFSI 190, 249 and 252 HP; S4 quattro 354 HP; mild hybrid 35 TFSI 150 HP, 40 TFSI 190 and 204 HP, 45 TFSI 245 to 265 HP |
|---|---|
| Spark plugs (aftermarket) | B8: NGK 1675 (platinum, 16 mm hex, M14x1.25, 19 mm reach); NGK 93322 (platinum, M14x1.25); NGK 94833 (platinum, 26.5 mm reach); NGK 94460 (platinum); NGK 5757 (platinum); Bosch 0 241 245 673 (gap 0.7 mm, 26.5 mm reach); Bosch 0 241 245 677 (gap 0.65 mm); Denso IK20TT (iridium centre, platinum earth) |
| Genuine (OE) numbers quoted | B8 none quoted; B9 Kamoka 7090007 quotes OE 06K 905 601 B |
| Fitment notes | The B8 list is almost entirely M14x1.25, 16 mm hex plugs, with NGK's platinum and iridium lines and no engine codes against individual plugs. The B9 list adds M12x1.25 plugs (NGK 95463, 93560, Beru Z365, Champion OE244) alongside M14x1.25 ones, so the plug depends on the engine. |
Audi A4 Spark Plugs: A Cheap Part That Causes Expensive-Feeling Problems
The Audi A4's spark plugs rarely fail dramatically; they just quietly degrade, showing up as a rougher idle or slightly blunted acceleration that gets blamed on other things. The part costs next to nothing, which paradoxically makes it one of the most commonly neglected items under the bonnet.
Audi A4 Spark Plugs: What They Do
On the Audi A4, the compressed fuel-air mixture in each cylinder is ignited by the spark plugs, and their condition feeds directly into combustion efficiency, fuel economy and how smoothly the engine runs. Only petrol engines use them; diesels rely on compression alone.
Audi A4 Spark Plugs: Generations, Engines & Spark Plug Count
| Diesel variants (35 TDI, 40 TDI and similar) | Not applicable — diesel engines use compression ignition and have no spark plugs at all |
|---|---|
| Petrol four-cylinder (35 TFSI, 40 TFSI, 45 TFSI) | 4 spark plugs — one per cylinder |
| S4 (3.0 TFSI V6) | 6 spark plugs — a genuinely different engine family from the standard four-cylinder units, not a bigger version of the same engine |
Audi A4 Spark Plugs: Watch: Replacing It
B8 saloon; for B9 use https://www.youtube.com/watch?v=5WqoViGBVsI (A4/A5/Q5 B9 2.0T coil and plug DIY)
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A Genuinely Honest, Real Account Worth Knowing — Audi A4 Spark Plugs
If a coil pack replacement hasn't resolved a persistent misfire on a specific cylinder, this is genuinely worth knowing: one documented case, on a car just three years old, saw exactly this happen — a coil pack was replaced for a misfire on a specific cylinder, yet the misfire persisted. Replacing the spark plugs afterward revealed noticeable carbon buildup on all of them, with fuel still present specifically on the misfiring cylinder's plug, pointing toward the fuel injector on that cylinder as the actual underlying cause rather than the coil at all. It's genuinely worth knowing a coil replacement not fixing the fault doesn't necessarily mean you need a different coil — it can point toward the plugs or injectors instead.
It's also genuinely worth knowing a common, easily overlooked mistake during a DIY coil replacement: failing to fully click the rear coil pack connectors back into place is a frequently documented cause of a misfire appearing immediately after fitting new coils, worth double-checking every connector is properly seated, particularly the rear ones which are harder to see and reach. It's also worth knowing that mixing coils bought at different times from different sources, rather than replacing them all together from a single reputable supplier, has been documented causing ongoing, hard-to-diagnose misfires.
Audi A4 Spark Plugs: Warning Signs, DIY Difficulty & Aftermarket Advice
These are the same regardless of make or model — see our full Spark Plugs Guide for symptoms of worn plugs, why matching your exact plug specification matters, and trusted brands to buy from.
More Audi Spark Plugs
The same part, covered across other Audi models.