P0308 on Audi
Cylinder 8 Misfire Detected
P0308 on Audi vehicles indicates cylinder 8 misfire detected. Au7o has documented this code across 4 Audi models — most commonly on A8, R8, RS4. P0308 means the engine computer detected a misfire on cylinder number 8 — that cylinder is failing to combust properly or at the correct time. The PCM identifies it by monitoring crankshaft speed variations as cylinder 8 fires. Misfires waste fuel, increase emissions, and can overheat and damage the catalytic converter, so a hard misfire may cause a flashing check engine light. Typical symptoms include rough idle, vibration, hesitation, and reduced power. Typical repair costs on Audi range from $350 to $1,800, depending on the specific model and root cause.
Common Causes of P0308
- •Worn, fouled, or incorrectly gapped spark plug on cylinder 8
- •Failed ignition coil or coil-on-plug for cylinder 8
- •Faulty, clogged, or leaking fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Damaged spark plug wire or boot (on applicable engines)
- •Carbon buildup or sticking valve
P0308 on Audi by Model
Audi A8(1 issue)
- Severe Carbon Buildup on Intake Valves2011-2023
All A8 models with direct-injection engines (3.0T, 4.0T, 60 TFSI) suffer from severe carbon buildup on intake valves. In direct-injection engines, fuel bypasses the intake valves, leaving them exposed only to oil vapors from the PCV system. These vapors bake onto valve backs as hard carbon deposits over 60,000-100,000 miles. Carbon restricts airflow, causing rough idle, misfires, hesitation, and power loss. The high-performance engines in the A8 are particularly susceptible due to higher oil vapor pressure. The ONLY effective fix is walnut blasting every 60,000 miles. This is preventive maintenance, not optional. Failure to clean carbon can cause valve damage requiring engine replacement on the A8's expensive V6/V8 engines.
Audi R8(1 issue)
- Ignition Coil Pack Failure Causing Misfires2008-2023
The coil-on-plug ignition coils on both the 4.2 V8 and 5.2 V10 are a recurring weak point, often failing between 50,000 and 80,000 miles. A failing coil produces a weak or inconsistent spark, triggering cylinder misfires, rough idle, hesitation and a check-engine light. Owners frequently report that oil weeping from valve-cover gaskets or spark-plug tube seals collects in the plug wells and accelerates coil breakdown by overheating and shorting the coil. Because the V8 has 8 coils and the V10 has 10, chasing one bad coil at a time is common but shops recommend replacing them as a set.
Audi RS4(1 issue)
- 2007-2008 RS4 Deposit-Related Cold-Start Misfire - Diagnose Before Cleaning2007-2008
Audi guidance documents that fuel-related deposits can cause a rough cold start, hesitation, reduced performance and misfire faults. For the B7 RS4 4.2L FSI V8, Audi TSB 2022030/2 treats P0300 and cylinder-misfire faults as a diagnostic starting point and first distinguishes injector deposits from other causes. These symptoms do not by themselves prove intake-valve buildup, and Audi does not specify a recurring 30,000-60,000-mile cleaning interval in the cited guidance.
Audi S7(1 issue)
- Ignition Coil Pack Failure Causing Misfires (4.0T V8)2013-2018
The eight individual coil-on-plug ignition coils on the 4.0T V8 are a recurring misfire source as they age, especially on tuned cars where higher cylinder pressures stress the spark. A failing coil produces a cylinder-specific misfire (P030X) and a flashing or steady check engine light. Owners and shops commonly diagnose by swapping a suspected coil to a different cylinder — if the misfire code follows the coil, the coil is confirmed bad. This is distinct from the already-documented fuel-injector deposit misfires and carbon-buildup issues: here the root cause is the ignition coil itself (or its companion spark plug), not fueling.
Looking for P0308 on a different make?
View P0308 across all makes →Frequently Asked Questions
What does P0308 mean on Audi?▼
P0308 stands for "Cylinder 8 Misfire Detected." P0308 means the engine computer detected a misfire on cylinder number 8 — that cylinder is failing to combust properly or at the correct time. The PCM identifies it by monitoring crankshaft speed variations as cylinder 8 fires. Misfires waste fuel, increase emissions, and can overheat and damage the catalytic converter, so a hard misfire may cause a flashing check engine light. Typical symptoms include rough idle, vibration, hesitation, and reduced power. On Audi specifically, this code is documented across 4 models.
What causes P0308 on Audi vehicles?▼
Common causes on Audi: Worn, fouled, or incorrectly gapped spark plug on cylinder 8, Failed ignition coil or coil-on-plug for cylinder 8, Faulty, clogged, or leaking fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0308 on a Audi?▼
Repair costs on Audi range from $350 to $1,800, depending on the specific model and root cause.
Which Audi models have P0308 documented?▼
Au7o has documented P0308 on 4 Audi models: A8, R8, RS4, S7.