P0304 means your engine's computer has identified consistent misfires in cylinder 4. On most inline-4 engines, cylinder 4 is at the rear near the firewall, which can make access slightly harder. The fault is isolated to that cylinder's ignition, fuel, or compression system.
DTC/P0304·SEAT
P0304 on SEAT: Causes, Symptoms and Fix Cost
Quick Answer
High SeverityNot safe to driveSEAT
P0304 on a SEAT means your engine's computer has identified consistent misfires in cylinder 4. On most inline-4 engines, cylinder 4 is at the rear near the firewall, which can make access slightly harder. The fault is isolated to that cylinder's ignition, fuel, or compression system.
Repair cost on SEAT€37 - €2205
What does P0304 mean on a SEAT?
SEAT Leon
2005-2024The Leon shares VW Group EA211 and EA888 engines. The 1.4 TSI (EA211) in Mk3 models can develop ignition coil failures on any cylinder. Cylinder 4 misfires on the 2.0 TSI Cupra are often traced to carbon buildup from high-performance driving.
What causes P0304 on a SEAT?
Beyond the generic causes listed on the main P0304 page, these are the SEAT-specific patterns we see most often:
SEAT LeonIgnition coil failure on 1.4 TSI (EA211)
SEAT LeonCarbon buildup on 2.0 TSI Cupra under hard driving
How to diagnose P0304 on a SEAT with OBD2
Follow these steps to pinpoint the root cause of P0304:
- Retrieve freeze-frame data and note any companion misfire codes (P0300-P0303) that may indicate a wider problem
- Swap the ignition coil from cylinder 4 with cylinder 1 or 2, clear codes, and test drive. If the misfire code follows the coil, replace it
- Remove and inspect the spark plug on cylinder 4. On inline-4 engines, cylinder 4 is nearest the firewall, so a spark plug socket with an extension may be needed
- Verify the fuel injector on cylinder 4 is receiving its electrical pulse using a noid light. Also check for visible fuel leaks at the injector seal
- If ignition and fuel are ruled out, perform a compression and leak-down test on cylinder 4 to check for valve seating issues or ring wear
How much does P0304 cost to fix on a SEAT? (EUR)
Estimated repair costs on a SEAT (SEAT parts and labour typically run 5% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0304 on SEAT
These codes commonly cluster with P0304 on SEAT vehicles:
FAQ: P0304 on SEAT
What does P0304 mean on my car?
P0304 tells you that the engine control module has detected repeated misfires on cylinder 4. The ECU counts misfires by monitoring tiny variations in crankshaft speed and flags the code when cylinder 4 misfires exceed the allowed threshold.
Is cylinder 4 hard to access?
On inline-4 engines, cylinder 4 is typically closest to the firewall at the rear of the engine bay. Access can be tighter, especially for spark plugs and coils. On some vehicles you may need to remove an engine cover or intake components.
Can a P0304 misfire damage my engine?
The misfire itself does not usually damage the engine block, but unburned fuel washing the cylinder walls can dilute oil and accelerate ring wear over time. The bigger immediate risk is catalytic converter damage from overheating.
Why did P0304 appear after changing spark plugs?
This is usually caused by an incorrectly gapped plug, the wrong plug type for your engine, a plug not seated properly, or a damaged ignition coil boot. Remove the cylinder 4 plug, verify the gap and part number, and re-seat it.
Should I replace all ignition coils if only cylinder 4 is misfiring?
It is not strictly necessary, but if the vehicle has high mileage (over 100,000 km) and the other coils are original, replacing the full set is a good preventive measure. Coils of the same age tend to fail in sequence.
Looking for the full P0304 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0304 guideSkanyx · SEAT
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