P0304: Cylinder 4 Misfire Detected
The ECM detects crankshaft speed drop on Cylinder #4. Cylinder 4 is closest to the transmission bellhousing on transverse inline 4-cylinder vehicles.
Driveability & Safety Advisory
Drive short distances only to repair shop. Avoid rapid acceleration.
Official Manufacturer TSB Advisories
Factory Condition: Valve cover spark plug tube seal on Cylinder 4 leaks oil into spark plug well, shorting out ignition coil boot.
Physical Component Location & Service Access
Cylinder #4 is located closest to the transmission bellhousing on 4-cylinder engines.
Electrical Specifications & Live PID Benchmarks
Scan Tool Live Data Targets
Digital Multimeter (DMM) Specs
Documented Model-Specific Case Studies
Root Cause: Cylinder 4 ignition coil internal capacitor failure.
Verified Fix: Replace Cylinder 4 ignition coil.
Technician Inspection & Testing Workflow
Remove Cylinder 4 coil: Check for engine oil in the spark plug well.
Perform coil swap test with Cylinder 1.
Check spark plug gap.
Recommended Diagnostic Tools & Verified Parts
BlueDriver Bluetooth Pro OBDII Scan Tool
Wireless sensor telemetry & enhanced diagnostics (Engine, ABS, Airbag). Delivers verified vehicle repair reports.
Autel AutoLink AL519 / AL319 OBD2 Scanner
Color screen standalone scanner. One-click I/M emissions readiness status, freeze-frame data, live DTC reset.
Ram-Pro Inline Engine Ignition Spark Tester & Gap Gauge
Quickly verify if spark plug coils are firing with high-intensity visual spark indicator. Includes electrode gap measure tool.
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Cost Breakdown
Tools & Parts Matrix
Diagnostic Questions & Answers
Why was there oil on my Cylinder 4 spark plug?
A leaking spark plug tube seal in the valve cover allows oil to submerge the plug, which grounds the spark voltage and causes misfires.