P0304 on Ford: Causes, Symptoms and Fix Cost
Quick Answer
Not safe to drive
P0304 on a Ford means your engine's computer has identified consistent misfires in cylinder 4. Where cylinder 4 sits depends on how the engine is mounted: on a lengthwise (longitudinal) inline-4, usual in rear-wheel-drive cars, it is the cylinder nearest the firewall, while on a transverse engine, usual in front-wheel-drive cars, it is at the gearbox end. The fault is isolated to that cylinder's ignition, fuel, or compression system.
- Severity
- High · Misfire
- Typical repair cost, all makes
- €35-€2100
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Ford and Skanyx tells you what P0304 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0304 mean on a Ford?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Ford models that log P0304.
Ford Focus
2005-2022
The Focus has a transverse engine, so on the 1.6 Ti-VCT and 2.0 Duratec cylinder 4 is at the gearbox end of the engine, not near the firewall. The 1.0 EcoBoost 3-cylinder does not have a cylinder 4. The 2.0 GDI engine can develop carbon buildup affecting cylinder 4.
What causes P0304 on a Ford?
Beyond the generic causes listed on the main P0304 page, these are the patterns noted for Ford models:
Carbon buildup on 2.0 GDI intake valves
: Ford Focus
Ignition coil failure on 1.6 Ti-VCT, especially at higher mileage
: Ford Focus
How to diagnose P0304 on a Ford with OBD2
- 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 a longitudinal inline-4 it is nearest the firewall, on a transverse one it is at the gearbox end, and 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 Ford? (EUR)
Estimated repair costs for P0304 in EUR, compiled across makes. Ford costs typically sit in the middle of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace spark plug (cylinder 4) | €5–€25 | €30–€100 | €35–€125 | Easy |
| Replace ignition coil (cylinder 4) | €25–€130 | €30–€110 | €55–€240 | Easy |
| Replace fuel injector (cylinder 4) | €50–€200 | €70–€220 | €120–€420 | Moderate |
| Valve or compression repair | €200–€700 | €400–€1400 | €600–€2100 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0304
These codes are often seen alongside P0304 or point to related issues, on any make:
Looking for the full P0304 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0304 guide