P0307
Cylinder 7 Misfire Detected
Your engine is not firing correctly in cylinder 7. This can cause a rough idle, shaking under load, poor power, and catalytic-converter damage if you keep driving. On trucks and SUVs with V8 engines, the right fix is usually to swap and test the spark, coil, injector, and compression branches before replacing parts.
- SEV
- 4/5
- DRIVE
- CAUTION
- DIY
- $20–$250
- SHOP
- $150–$800
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty spark plug in cylinder 7
- Bad ignition coil or coil boot on cylinder 7
- Fuel injector problem on cylinder 7
Typical repair cost
DIY usually runs $20–$250. Typical shop repair lands around $150–$800, depending on the root cause.
01 / Definition
P0307 means the engine computer has detected a misfire on cylinder 7. The misfire may be occasional or continuous, and the cause can be ignition, fuel delivery, air leak, compression, or wiring related. If the misfire is severe, the ECM may flash the check engine light to warn of possible catalytic converter damage.
02 / Drive status
With caution. You may be able to move the vehicle short distances, but an active misfire can quickly damage the catalytic converter and can turn into a no-power or no-start condition. If the engine is shaking badly, the check engine light is flashing, or power drops under load, stop driving and diagnose it right away.
03 / Symptoms
- Rough idle
- Engine shaking or vibration
- Loss of power
- Poor fuel economy
- Check engine light on
- Flashing check engine light during severe misfire
- Hard starting or long cranking
- Fuel smell from exhaust
- Surging or hesitation under acceleration
04 / Causes
| 1 | Faulty spark plug in cylinder 7 | high |
|---|---|---|
| 2 | Bad ignition coil or coil boot on cylinder 7 | high |
| 3 | Fuel injector problem on cylinder 7 | medium |
| 4 | Vacuum leak or intake air leak affecting cylinder 7 | medium |
| 5 | Worn or damaged spark plug wire or connector, if equipped | medium |
| 6 | Low compression from worn engine components, leaking valve, or head gasket issue | medium |
| 7 | Dirty or contaminated fuel | low |
| 8 | Wiring, connector, or ECM driver issue for cylinder 7 | low |
05 / Diagnostic sequence
- 01Check whether the check engine light is flashing. If it is, avoid driving until the cause is found because catalyst damage can happen quickly.
- 02Scan for related codes, including fuel trim, injector, ignition, or lean condition codes, and save freeze-frame data so you know the load and RPM where the misfire was detected.
- 03Inspect and replace the spark plug for cylinder 7 if it is worn, fouled, oil-soaked, or damaged.
- 04Swap the cylinder 7 ignition coil with another cylinder and see whether the misfire moves with it before buying new ignition parts.
- 05Inspect the coil connector, spark plug boot, and wiring for corrosion, damage, or loose pins.
- 06Check the fuel injector for cylinder 7 using listen test, resistance test, or injector balance test.
- 07Look for vacuum leaks, intake gasket leaks, or unmetered air near the affected cylinder, especially if the misfire is worse at idle or on one bank.
- 08Perform a compression test or leak-down test if ignition and fuel checks do not solve the problem.
06 / Repairs
| 1 | Replace the spark plug for cylinder 7 if it is worn or fouled | $20–$80 |
|---|---|---|
| 2 | Replace the ignition coil, coil boot, or spark plug wire for cylinder 7 if defective | $50–$250 |
| 3 | Repair or replace the cylinder 7 fuel injector or injector connector | $100–$450 |
| 4 | Repair vacuum leaks, intake leaks, or damaged hoses/gaskets | $50–$400 |
| 5 | Repair internal engine compression issues if found | $500–$3,000+ |
07 / Related codes
08 / FAQ
Can I keep driving with P0307?
Only for short, cautious trips if the engine runs normally and the light is not flashing. If it is shaking, losing power, or the light is flashing, stop driving and diagnose it immediately.
What is the most common cause of P0307?
A worn spark plug or a bad ignition coil on cylinder 7 is usually the first thing to check.
Will P0307 go away on its own?
Sometimes the code may clear temporarily, but the underlying problem usually remains and the misfire can return.
Can a bad injector cause P0307?
Yes. If cylinder 7 is not getting the right amount of fuel, it can misfire and set this code.
Does P0307 always mean a bad coil pack?
No. A coil is common, but a spark plug, injector, vacuum leak, wiring fault, or low compression can trigger the same cylinder-specific misfire. Swap-test results are usually the fastest way to separate the ignition branch from the rest.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.