P0303 on Peugeot: How to Diagnose & Fix
Cylinder 3 Misfire Detected
1 Peugeot model · 1 documented issue · $350-$900 repair
P0303 on Peugeot by model: symptoms, diagnosis and fix
Because the turbocharged 1.6 THP (EP6DT/EP6CDT/EP6DTS) injects fuel directly into the cylinder, no fuel washes over the backs of the intake valves; oil vapour from the PCV system bakes onto the valves and ports as hard carbon. Deposits typically become symptomatic between 50,000 and 80,000 km, progressively restricting airflow and causing rough cold idle, cold-start misfires, poor throttle response and higher fuel consumption.
Common Symptoms
- Rough idle, especially when cold
- Random misfires on cold start
- Hesitation and poor throttle response
- Noticeable loss of power
- Increased fuel consumption
How to Fix
Walnut-shell blasting of the intake ports and valves is the accepted fix (roughly $350-900 at independent specialists; dealer quotes can be far higher) and is worth repeating preventively every 50,000-60,000 km. Quality fuel and regular oil changes slow, but do not prevent, re-accumulation.
Sources for this issue (3)
P0303 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0303 mean on a Peugeot?
P0303 stands for "Cylinder 3 Misfire Detected." This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. On Peugeot it is documented across 1 model: 308.
What are the most common causes of P0303?
The most common causes of P0303 are: Worn or fouled spark plug in cylinder 3, Failed or weak ignition coil on cylinder 3, Bad spark plug wire or boot (where applicable), Clogged or leaking fuel injector for cylinder 3, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket), Wiring or connector fault at the coil or injector. The specific cause varies by vehicle.
How much does it cost to fix P0303 on a Peugeot?
Published repair estimates on Peugeot range from $350 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0303 on a different make?
View P0303 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.