P0307: Cylinder 7 Misfire Detected
On a V8 or larger engine, the computer has caught cylinder 7 misfiring repeatedly.
What P0307 means
You will only see P0307 on engines with at least seven cylinders, so it almost always shows up on V8 trucks, SUVs and performance cars. As with other cylinder codes, the computer is reading crank speed and matching the dips to cylinder 7 in the firing order. Where cylinder 7 sits depends on the maker; on many GM and Chrysler V8s it is near the back, while Ford numbers its banks differently. On some V8 engines with cylinder deactivation, lifter problems can cause a misfire on specific cylinders, so a ticking noise along with the code is worth mentioning to your mechanic. The normal diagnosis is still a coil swap, a plug check and an injector test, followed by a compression test if needed. Rear cylinders can be cramped, so labor may run higher than you expect. Keep trips short until it is fixed, because a misfiring V8 sends a lot of unburned fuel into the converters.
Common symptoms
- Check engine light on, or flashing when the misfire is bad
- Rough or shaky idle
- Hesitation or jerking when you accelerate
- Loss of power, especially going uphill or merging
- Worse gas mileage
Most common causes
- Bad ignition coil or coil boot on cylinder 7
- Worn or fouled spark plug
- Fuel injector fault
- Exhaust manifold or intake gasket leak near the rear cylinders
- Collapsed lifter or worn cam lobe
- Low compression
What to check yourself first
Check your engine diagram, since cylinder 7 location varies between GM, Ford and Chrysler V8s. Swap the cylinder 7 coil with another and clear the code. Listen for a ticking noise near that cylinder, which can point to a lifter or exhaust leak.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace ignition coil | $238-$320 | V8s usually have one coil per cylinder, so only the bad one needs replacing. |
| Replace spark plugs | $288-$399 | Rear cylinders on trucks can be tight to reach, which raises labor. |
| Replace fuel injector | $768-$953 | Done when the injector fails a balance test. |
| Check engine light diagnosis at a shop | $125-$183 | A shop may check for a collapsed lifter if there is also a ticking noise. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
Related repair guides
- Dodge Durango Misfiring or Ticking? HEMI Lifter Failure, Pentastar Head Problems and What Repairs Cost
- Honda Pilot Misfire Codes P0301-P0304? The VCM Oil-Fouling Problem and What Honda Covers
- Hyundai Elantra Misfiring or Flashing Check Engine Light? Plug and Coil Costs, Plus the Engine Recalls to Check First
- Ram 1500 Hemi Tick and Misfire: Spark Plug, Coil or Lifter? How to Tell (and What Each Costs)
Related codes
- P0300 Random/Multiple Cylinder Misfire Detected
- P0308 Cylinder 8 Misfire Detected
- P0305 Cylinder 5 Misfire Detected
- P0430 Catalyst System Efficiency Below Threshold (Bank 2)
- P0207