Understanding and Fixing the P0308 Code: Cylinder 8 Misfire Issues

Is your engine running rough or lacking power? A P0308 code, indicating a "Cylinder 8 Misfire Detected," means cylinder 8 isn’t firing correctly, which can harm your engine if not addressed. This guide explains the causes, symptoms, and steps to fix this issue using an OBD2 scanner, keeping your vehicle running smoothly.

1. What Is a Cylinder 8 Misfire?

The P0308 code signals a misfire in cylinder 8, where combustion is incomplete or absent, disrupting engine performance. The Powertrain Control Module (PCM) detects this by monitoring crankshaft speed variations, typically in V8 or larger engines. If unresolved, it can lead to catalytic converter damage or engine wear (OBD-Codes).

2. Signs of Cylinder 8 Trouble

• Check Engine Light: Illuminates on the dashboard.
• Rough Idling: Engine shakes or feels uneven.
• Weak Acceleration: Sluggish response during acceleration.
• Increased Fuel Consumption: Poor fuel economy.
• Stalling or Hesitation: Engine may stall or hesitate under load.

3. Causes of a Cylinder 8 Misfire

• Faulty Spark Plug or Wiring: Worn or damaged spark plug/wires in cylinder 8 (CarParts).
• Defective Ignition Coil: Failing coil for cylinder 8.
• Fuel Injector Issues: Clogged or leaking injector.
• Low Compression: Worn piston rings or valves in cylinder 8.
• Vacuum Leak: Disrupts air-fuel ratio.
• PCM Fault: Rare issue with incorrect PCM signals.

4. How Serious Is P0308, and Can I Drive?

P0308 is moderately serious. A misfire can damage the catalytic converter, increase emissions, and cause engine wear over time. Short drives are usually okay, but avoid long trips or heavy loads until repaired (RepairPal).

5. Diagnosing P0308 with an OBD2 Scanner

A reliable OBD2 scanner is key to diagnosing P0308:

1. Connect the scanner to the OBD-II port (typically under the dashboard).
2. Select your vehicle’s make and model.
3. Read the P0308 code and check for related codes.
4. Monitor live data for injector and ignition coil performance.
5. Inspect spark plugs, coils, and fuel system components.

6. Steps to Fix a Cylinder 8 Misfire

1. Replace Spark Plugs/Wires: Install new plugs or wires for cylinder 8.
2. Test/Replace Ignition Coil: Swap out a faulty coil.
3. Clean/Replace Fuel Injector: Address clogs or leaks.
4. Check Compression: Test cylinder 8 for low compression.
5. Repair Vacuum Leaks: Fix leaks in the intake system.
6. Update PCM: Reset or update the PCM if necessary.

7. Repair Costs in the U.S.

Using an OBD2 scanner ensures accurate diagnosis, reducing unnecessary repair costs.

8. Tips to Prevent Future Misfires

• Replace Spark Plugs Regularly: Every 30,000 miles.
• Inspect Ignition Coils: Check during routine maintenance.
• Maintain Fuel System: Clean injectors annually.
• Monitor Compression: Test every 60,000 miles.
• Check for Leaks: Regularly inspect the intake system.

9. Why Use an OBD2 Scanner for Misfires?

• Comprehensive Diagnostics: Reads all OBD-II codes.
• Real-Time Data: Monitors injector and coil performance.
• Easy to Use: Suitable for DIYers and professionals.
• Fast Code Clearing: Resets codes post-repair.

10. Explore Related Diagnostic Guides

Learn more about engine and diagnostic issues with these guides:

• P0304: Cylinder 4 Misfire Detected
• P0305: Cylinder 5 Misfire Detecte
• P0261: Cylinder 1 Injector Circuit Low
• P0271: Cylinder 4 Injector Circuit High

Find diagnostic tools at iCarsoft-US.com.

11. Common Questions About P0308