Cylinder 7 Misfire Detected (P0307)
The P0307 code indicates that the engine's cylinder 7 is misfiring, meaning it is not contributing power properly. This can be caused by a faulty spark plug, ignition coil, fuel injector, or a mechanical issue like low compression. The misfire can lead to rough idling, reduced fuel economy, and potential damage to the catalytic converter if left unaddressed.
01. Most Common Causes
- Faulty spark plug or ignition coil on cylinder 7
- Clogged or faulty fuel injector on cylinder 7
- Vacuum leak or intake manifold gasket leak
- Low compression in cylinder 7 (worn piston rings, valves, or head gasket)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine runs rough, shakes, or hesitates
- Reduced power and acceleration
- Increased fuel consumption
03. Step-by-Step Diagnosis
Step 1: Scan for codes and note freeze frame data.
Step 2: Inspect spark plug and ignition coil on cylinder 7; swap with another cylinder to see if misfire moves.
Step 3: Check fuel injector on cylinder 7; listen for clicking or perform a balance test.
Step 4: Perform a compression test on cylinder 7 and compare to others.
Step 5: Inspect for vacuum leaks using a smoke machine or propane enrichment.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with a misfire, as it can damage the catalytic converter and other engine components. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost varies depending on the cause. A spark plug replacement is typically $50-$150, while an ignition coil or fuel injector can cost $150-$400. Compression repairs can be significantly more.