P0304: Cylinder 4 Misfire Detected
162 vehicles · 30 makes · $20-$20,000 repair
Most Reported On
P0304 is an OBD-II diagnostic trouble code meaning “Cylinder 4 Misfire Detected.” This code means the engine computer detected a misfire in cylinder number 4 — that cylinder isn't igniting its air-fuel mixture fully or at all. The system detects this by monitoring small changes in crankshaft rotation speed as each cylinder fires. You may feel a rough idle, shaking, hesitation or reduced power, and a persistent misfire can dump unburned fuel into the exhaust and overheat or damage the catalytic converter. Since it's pinpointed to one cylinder, the problem typically lies in that cylinder's spark, fuel, or compression. This code is most commonly reported on 2004-2012 Mazda RX-8, 2011-2019 Hyundai Sonata (Base, GL, GLS, LX, Limited, SE, SEL, SEL Plus, Sport), and 2008-2021 Volkswagen Golf (GTI, GTI Autobahn, GTI S, GTI SE, Golf R, R, R32), plus 159 other vehicles, with repair costs ranging from $20 to $20,000.
Common Causes
Typical Repair Cost
Based on 207 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0304, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (162)
Oil Consumption and Fouled Spark Plugs on 3.7L V6
Distributor internal shaft seal fails, oil leaks into cap and causes misfires + stalling
Distributor shaft seal leaks oil into cap, causes misfires (P0300-P0304) on 3.5L C35A
Intake Valve Carbon Buildup
Ignition Coil Failure
4.0T Direct Injection Carbon Buildup
4.0T Carbon Deposit Accumulation
3.0T Intake Valve Carbon Buildup
2.5T Five-Cylinder Carbon Buildup
Direct Injection Carbon Buildup
Direct Injection Carbon Buildup (Intake Valves)
Coil Pack Failure and Ignition Misfires on 1.8T Engines
Carbon Buildup on Intake Valves (2.0 TFSI Direct Injection)
Severe Carbon Buildup on Intake Valves (Direct Injection Engines)
2.7T Ignition Coil Pack Failure Causing Misfires and Flashing Check Engine Light
Severe Carbon Buildup on Intake Valves (Direct Injection)
Intake Valve Carbon Buildup (Direct Injection)
4.2L V8 Carbon Buildup on Intake Valves
Carbon Buildup on Intake Valves (2.9T Twin-Turbo V6)
4.2L V8 Carbon Buildup and High-Rev Issues
Severe Carbon Buildup on Intake Valves (4.0T V8)
Turbo Wastegate Rattle and Carbon Buildup
Direct Injection Carbon Buildup on Intake Valves
Carbon Buildup on Intake Valves (4.0T Twin-Turbo V8)
Carbon Buildup on Intake Valves (Direct Injection)
Severe Carbon Buildup Causing Valve Damage (3.0T TFSI)
Water Pump Failure (60k Mile Lifespan)
Severe Carbon Buildup on Intake Valves (3.0T)
Carbon Buildup on Intake Valves (Pre-Dual Injection EA888 Gen 3)
4.0T Carbon Buildup on Intake Valves
Severe Carbon Buildup on Intake Valves (Direct Injection)
Severe Carbon Buildup on Intake Valves
Carbon Buildup on Intake Valves (4.2 V8 FSI and 5.2 V10 FSI)
Severe Carbon Buildup on Intake Valves (2.5T 5-Cylinder)
Water Pump and Thermostat Housing Coolant Leaks
Intake Valve Carbon Buildup
High-Pressure Fuel Injector Issues
Valve Cover Gasket Oil Leak
Intake Valve Carbon Buildup
G80 S58 Engine Carbon Buildup on Intake Valves
S58 Intake Valve Carbon Buildup
S58 Intake Valve Carbon Buildup
Carbon Buildup on Intake Valves (Direct Injection Engines)
Direct Fuel Injector Failure (S55)
N54 Spark Plug & Ignition Coil Failure (135i / 1M)
N54 High-Pressure Fuel Pump (HPFP) Failure (135i / 1M)
S55 High-Pressure Fuel Injector Failure - F82/F83 M4
S63/S63TU Ignition Coil Premature Failure
N54 High Pressure Fuel Pump (HPFP) Failure - E89 Z4 sDrive35i/35is
S63/S63TU Valve Stem Seal Failure & Oil Consumption
Fuel Injector Failure - 428i/430i/435i/440i F32/F33/F36
Ignition Coil Pack Failure Causing Misfires and Check Engine Light on M52TU/M54 Engines
Carbon Buildup on Intake Valves (Direct Injection Engines)
LT4 Supercharged V8 Premature Engine Failure
AFM/DOD Lifter Failure - V8 Cylinder Deactivation System
3.6L V6 Timing Chain Stretch and Premature Failure
Northstar 4.6L V8 Head Bolt/Head Gasket Failure
Northstar 4.6L V8 Head Bolt/Head Gasket Failure
3.6L V6 Timing Chain Stretch - SRX
Northstar 4.6L V8 Head Bolt/Head Gasket Failure
3.6L V6 Timing Chain Stretch (ATS V6 models)
5.3L Vortec AFM Active Fuel Management Oil Consumption and Lifter Failure
5.3L V8 (AFM/DFM) collapsed/failed lifter causing ticking and cylinder misfire
Injector Wiring Harness Chafing (Duramax)
Cylinder Head Valve Seat Failure and Misfire on 3.5L/3.7L Inline-Five
L99 AFM Lifter Failure and Camshaft Damage on 6.2L Automatic Cars
AFM/DFM Lifter Failure (5.3L/6.2L V8)
HEMI 5.7L MDS Lifter and Camshaft Failure
Pentastar Cylinder Head Failure
Chronic Overheating - Multiple Causes
Cooling System Failures (3.3L/3.8L V6)
Head Gasket Failure (Especially Turbo Models)
Turbocharger Failure (GT/Turbo Models)
3.6L Pentastar Engine Stalling and Head Gasket Failure
3.5L V6 Head Gasket Failure and Overheating
5.7L HEMI MDS Lifter Tick and Camshaft Failure
HEMI MDS Lifter Tick
HEMI MDS Lifter Tick
Pentastar V6 Rocker Arm/Lifter Tick
HEMI Lifter/MDS Tick
Pentastar V6 Rocker Arm/Lifter Tick
Cooling System Failures (3.3L/3.8L V6)
Engine Overheating - Thermostat Housing Debris
Head Gasket Failure
2.4L Electronic Throttle Body Failure
Gen 1 V10 Head Gasket Failure
Rod Bearing Failure from Oil Starvation (Track Use)
3.6L Pentastar V6 Left Cylinder Head Failure (Misfire on Cylinders 2/4/6)
2.3L EcoBoost Head Gasket Failure and Coolant Intrusion
2.0L Direct Injection Carbon Buildup on Intake Valves
1.5L EcoBoost Coolant Intrusion into Cylinders - Engine Block Porosity
Fuel Injector Failure and Rough Running (EcoBlue Diesel)
2.0L EcoBoost Coolant Intrusion - Open-Deck Block Failure
1.6L EcoBoost Engine Overheating and Coolant Loss - Recall 14S11
1.5L EcoBoost 3-Cylinder Coolant Loss and Engine Failure
Triton 2-Valve Spark Plug Blow-Out from Cylinder Head
EcoBoost Coolant Intrusion into Cylinders
Ignition Coil Failure and Misfires (2.5L/1.6L)
5.4L 2-Valve Spark Plug Blow-Out From Cylinder Head
Ignition Coil Pack Failure
4.6L 2-Valve Spark Plug Ejection/Breakage
2.0L SPI Head Gasket Failure
1.5T Earth Dreams Direct Injection Carbon Buildup on Intake Valves
Fuel Injector Debris Causing Misfires and Catalyst Codes
11th Gen 2.0T Direct Injection Carbon Buildup and Idle Vibration
Ignition Coil Failure
Idle and Stalling Problems
Spark Plugs Backing Out - Coil Pack Melting and Engine Damage
Cold-Start Rough Idle / Vibration on 1.5L Turbo (Linked to Oil Dilution & Misfire)
1.5L Turbo (L15BE) Engine Oil Dilution — Fuel in Oil, Overfilled Dipstick, Gas Smell in Cabin
EGR System Clogging (Lean Burn Engine)
Valve Cover Gasket and Spark Plug Tube Seal Oil Leaks Causing Misfires
Timing Belt and Water Pump Neglect Leading to 3.2L V6 Engine Damage
Distributor Internal Coil and Igniter Failure (4th Gen)
Theta II Engine Seizure/Failure
Theta II Engine Seizure Due to Connecting Rod Bearing Failure
Excessive Oil Consumption - 2.4L GDI Engine
Nu Engine Bearing Failure and Seizure
Fuel Injector Failure Causing Misfire, Rough Running, and Check Engine Light
Valve Cover Gasket Oil Leaks Onto Spark Plug Wells and Exhaust Manifold
HEMI Engine Tick/Lifter Noise
3.7L V6 Exhaust Manifold Crack / Valve Cover Oil Leaks
3.6L Pentastar V6 left cylinder head failure / engine tick (early build)
Ignition Coil Rail Failure Causing Misfire on 4.0L
Intake Valve Carbon Buildup (GDI Engines)
Fuel Injector Failure and Engine Stalling
SmartStream G2.5 GDI Engine Piston Ring/Oil Consumption Issue
Timing Belt Neglect Leading to Bent Valves and Sudden No-Start on 1.6L Engines
Ignition Coil and Plug Wire Failure Causing Misfire, Hesitation, and Check Engine Light
Ignition Coil Pack Failure Causing Misfire
Coil-on-Plug Ignition Coil Failure and Misfires (4.6L V8)
2.7L EcoBoost Excessive Oil Consumption from Faulty Valve Guides
Navigator 5.4L 3V Triton Spark Plug Breakage on Removal
Apex Seal Failure / Compression Loss
Crankshaft Position Sensor Failure (NB)
Carbon Buildup on Direct Injection Intake Valves
Carbon Buildup on Intake Valves (Skyactiv)
Ignition Coil Failure and Misfires
SkyActiv-G Intake Valve Carbon Buildup (Direct Injection)
Skyactiv 2.0L Intake Valve Carbon Buildup
N14/N18 Turbo Engine Timing Chain Catastrophic Failure
Direct Injection Carbon Buildup on Intake Valves
N12/N16 Timing Chain Tensioner Failure
Intake Valve Carbon Buildup from Direct Injection
Carbon Buildup on Intake Valves (Direct Injection) Causing Misfires/Power Loss
VVEL Solenoid Failure (VK56VD Engine)
2.5L Pre-Catalyst Breakdown Causing Excessive Oil Consumption and Engine Damage
Ignition Coil Failure
Excessive Oil Consumption (QR25DE)
Ignition Coil Failure (VQ35DE)
6.7L Cummins Exhaust Brake Actuator and VGT Turbo Issues
HEMI Lifter/Camshaft Failure
MDS Lifter Failure and Hemi Tick (5.7L)
5.7L HEMI MDS Lifter Failure
Head Gasket Failure
EJ253 Head Gasket Failure (External Leak)
EJ25 Head Gasket Failure
EJ25 Head Gasket Failure
Spun Rod Bearing Failure (EJ257)
Head Gasket Issues
FA20 Valve Spring Recall - Engine Stalling Risk
EZ36 Timing Chain Stretch and Guide Wear
EJ257 Piston Ringland Failure
EZ30 3.0L H6 Head Gasket Leak
Valve Spring Recall - Engine Stall Risk
EGR Valve and Intake Manifold Carbon Buildup
Water Pump Leak and Failure (2GR-FE)
1NZ-FXE Head Gasket Failure and EGR Cooler Issues
G16E-GTS Head Gasket Seepage Under Hard Use
1.5L 1NZ-FE Valve Cover Gasket and Oil Filler Cap Leak
Intake Manifold Gasket Vacuum Leak Causing Cold-Start Rough Idle and Lean Codes
2AZ-FE Excessive Oil Consumption From Piston/Ring Wear
2.4L 2AZ-FE Head Gasket and Head Bolt Thread Failure
2AZ-FE Excessive Oil Consumption from Piston/Ring Wear
Excessive Oil Consumption from 1ZZ-FE Piston Ring Wear
FA20 Valve Spring Recall (Campaign E0G/17V-587)
Valve Spring Recall (Early Production)
Direct Injection Carbon Buildup on Intake Valves
Intake Valve Carbon Buildup
2.5L 5-Cylinder Ignition Coil Pack Failure
Ignition Coil Failure
EA211 1.5T Engine Ticking and Fuel Injector Noise
EA888 Gen 3 Intake Valve Carbon Buildup (GDI)
Ignition Coil Pack Failure (1.8T/2.0)
2.0L Ignition Coil Pack Failure
Direct Injection Carbon Buildup on Intake Valves
Ignition Coil Pack Cracking and Misfires
EA888 Direct-Injection Carbon Buildup on Intake Valves
FAQ
What does P0304 mean?
P0304 stands for "Cylinder 4 Misfire Detected." This code means the engine computer detected a misfire in cylinder number 4 — that cylinder isn't igniting its air-fuel mixture fully or at all. The system detects this by monitoring small changes in crankshaft rotation speed as each cylinder fires. You may feel a rough idle, shaking, hesitation or reduced power, and a persistent misfire can dump unburned fuel into the exhaust and overheat or damage the catalytic converter. Since it's pinpointed to one cylinder, the problem typically lies in that cylinder's spark, fuel, or compression.
What are the most common causes of P0304?
The most common causes of P0304 are: Worn or fouled spark plug in cylinder 4, Failed or weak ignition coil on cylinder 4, Faulty spark plug wire or boot (where applicable), Clogged, stuck or leaking fuel injector for cylinder 4, Vacuum or intake air leak near that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket), Damaged wiring or connector at the coil or injector. The specific cause varies by vehicle.
How much does it cost to fix P0304?
Repair costs for P0304 range from $20 to $20,000, depending on the vehicle and root cause.
Which vehicles are affected by P0304?
Au7o has documented P0304 across 162 vehicle models from 30 manufacturers: Acura, Audi, BMW, Buick, Cadillac, Chevrolet, Chrysler, Dodge, Ford, GMC, Genesis, Honda, Hyundai, Jeep, Kia, Lexus, Lincoln, MINI, Mazda, Mercedes-Benz, Nissan, Peugeot, Pontiac, RAM, Saab, Saturn, Skoda, Subaru, Toyota, Volkswagen.
Sources (12)
- RecallNHTSA Recall 17V-224
- ForumHead Gasket Failure in 2.2 liter models - Subaru Outback Forums
- mediaSubaru Head Gasket Problems Explained - All Wheel Drive Auto
- ForumEj25 sohc 2000 ob head gasket - Ultimate Subaru
- mediaSubaru Head Gasket Problems Crucial Years - Automotive Body Care
- ForumEJ251 Head Gasket Problems - RS25
- ForumHead Gasket Problems Explained - RS25
- ForumHead gasket problem fixed in 2001 2.5 RS - RS25
- mediaJalopnik: These Subaru Model Years Were The Worst Affected By Head Gasket Problems
- manufacturerFel-Pro: Solving Subaru 2.5L Head Gasket Problems
- mediaHiRide: Subaru Outback Head Gasket Leak Symptoms Causes & DIY Diagnosis
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.