P0308 Technical Description
Cylinder 8 Misfire Detected
If you’re seeing the P0308 trouble code, you’re in the right place. This guide covers its meaning, symptoms, causes, and fixes to get your car running smoothly again.
I’ve tackled this issue numerous times, so you’re in good hands.
We’ll dive into what the P0308 code means and the typical symptoms you might notice. I’ll also walk you through common causes and practical fixes.
Alright, let’s get started and break it all down.
Key Takeaways
- P0308 code means a misfire in cylinder 8.
- Symptoms include rough idling, poor acceleration, and reduced fuel efficiency.
- Causes can be faulty spark plugs, ignition coils, or fuel injectors.
- Vacuum leaks, low fuel pressure, and engine issues can also trigger the code.
- Diagnosing involves checking spark plugs, ignition coils, and fuel injectors.
- Fixes include replacing faulty parts, repairing leaks, and ensuring proper fuel pressure.
Table of ContentsShow
What Does P0308 Trouble Code Mean?

The P0308 trouble code indicates that your vehicle’s engine control module (ECM) has detected a misfire in cylinder 8.
Misfires occur when the air-fuel mixture in the cylinder fails to ignite correctly, disrupting the combustion process.
This can lead to a variety of performance issues and, if left unresolved, can cause further damage to the engine.
When the ECM detects a misfire in cylinder 8, it triggers the P0308 code and illuminates the Check Engine Light.
This alert means the eighth cylinder isn’t firing as it should, causing your engine to run unevenly.
Misfires can be caused by several factors, including problems with the spark plug, ignition coil, fuel injector, or internal engine issues.
Common symptoms of a cylinder 8 misfire include rough idling, poor acceleration, and reduced fuel efficiency. You might also experience engine hesitation or stalling, particularly when the engine is under load or at idle.
These symptoms occur because the misfire disrupts the engine’s ability to maintain a smooth and consistent power output.
The primary components to check when diagnosing a P0308 code are the spark plug, ignition coil, and fuel injector for cylinder 8.
A worn or fouled spark plug, a faulty ignition coil, or a clogged or malfunctioning fuel injector can all cause a misfire.
Additionally, issues such as vacuum leaks, low fuel pressure, or even mechanical problems like a leaking head gasket or damaged valve can also trigger a misfire in cylinder 8.
Addressing the P0308 code promptly is crucial to prevent further damage. Ignoring it can lead to more severe engine issues, potentially increasing repair costs.
By understanding what the P0308 code means and its causes, you can take the necessary steps to diagnose and fix the problem, ensuring your engine runs smoothly again.
P0308 Trouble Code Symptoms
When your car has a P0308 trouble code, you’ll notice several key symptoms:
- Rough idling
- Poor acceleration
- Reduced fuel efficiency
- Engine hesitation
- Stalling, especially at idle or under load
- Illuminated Check Engine Light
P0308 Trouble Code Causes
Several factors can cause the P0308 trouble code. Here are the common causes:
- Faulty spark plug in cylinder 8
- Defective ignition coil
- Clogged or malfunctioning fuel injector
- Vacuum leak
- Low fuel pressure
- Leaking head gasket
- Damaged valve in cylinder 8
- Wiring issues related to cylinder 8’s ignition components
How To Fix A P0308 Trouble Code

Fixing a P0308 trouble code involves a few diagnostic steps and repair procedures. Here’s how to get started:
1. Scan for Codes
Use an OBD-II scanner to confirm the P0308 code and check for any other related codes.
2. Inspect the Spark Plug
Check the spark plug in cylinder 8 for wear or damage. Replace it if it’s fouled, worn, or damaged.
3. Check the Ignition Coil
Test the ignition coil for cylinder 8. Swap it with another cylinder’s coil to see if the misfire follows. Replace if faulty.
4. Examine the Fuel Injector
Inspect the fuel injector for cylinder 8. Look for clogs or malfunctions. Clean or replace the injector if necessary.
5. Inspect for Vacuum Leaks
Check for vacuum leaks around cylinder 8. Use a smoke machine or carb cleaner to identify any leaks and repair them.
6. Check Fuel Pressure
Test the fuel pressure to ensure it’s within the manufacturer’s specifications. Low fuel pressure can cause misfires.
7. Inspect the Head Gasket
Look for signs of a leaking head gasket, such as coolant in the oil or white smoke from the exhaust. Replace the gasket if needed.
8. Examine Valves and Cylinder
Inspect the valves in cylinder 8 for damage. A compression test can help identify any internal engine issues. Repair or replace as necessary.
9. Check Wiring
Inspect the wiring and connections related to the ignition coil, spark plug, and fuel injector in cylinder 8. Repair any damaged wires or poor connections.
10. Clear the Codes
After completing repairs, use the OBD-II scanner to clear the codes and test drive the vehicle to ensure the issue is resolved.
By following these steps, you can diagnose and fix the P0308 trouble code, ensuring your engine runs smoothly again.
Conclusion
Now you know what the P0308 trouble code means and how you can fix it.
Have you dealt with a cylinder misfire before?
Drop a comment below and share your experience or any tips!