An engine misfire is very dangerous for your engine. The misfire takes place due to insufficient combustion of the fuel and air mixture. When the vehicle powertrain control module (PCM) detects a misfire, it triggers a specific trouble code. When your PCM detects a misfire on cylinder 7, it triggers the diagnostic trouble code (DTC) P0307. This article mainly explains the P0307 code symptoms, its causes, and how to fix it.
P0307 Code Definition
The P0307 code stands for “Cylinder 7 Misfire Detected.”
What Does the P0307 Code Mean?
The P0307 code indicates that your powertrain control module (PCM) has detected a misfire on cylinder number 7.
Cylinder number 7 indicates not the 7th cylinder in the firing order, but the cylinder numbered “7” in the arrangement of cylinders on the engine.
Remember that the efficient burning of air and fuel is essential to engine operation. The combustion of the air-fuel mixture inside the engine cylinder generates power that is used to run the vehicle. A vehicle engine usually contains 4, 6, or 8 cylinders.
Without the proper combustion of the air-fuel mixture, the engine won’t run properly or won’t run at all.
Your PCM continuously records the working of all engine cylinders to ensure all cylinders are firing properly. Whenever any of these cylinders start misfiring, PCM triggers a code, and your check engine light starts flashing. The P0307 trouble code indicates that your vehicle engine cylinder number 7 is misfiring.
Anything from a bad spark plug to low fuel may cause the misfires. Therefore, as your vehicle engine starts misfiring, you should travel your car to the nearest workshop to fix the main issue. You shouldn’t ignore misfiring because it may cause engine damage or complete failure of the engine.
Symptoms of P0307 Code
When you drive your vehicle with P0307 code, it triggers one or more of the following symptoms:
- Check Engine Light illumination
- Jerking and vibration when driving
- Engine stalling
- The gas smell from the exhaust pipe
- Misfires
- Poor car acceleration
- A reduction in the engine power
- Poor fuel economy
- Rough idle
Causes of P0307 Code
The P0307 code is caused by one or more of the following causes:
- Faulty crankshaft sensor
- Low engine compression
- Faulty camshaft sensor
- Bad spark plugs in cylinder 7
- Low fuel pressure
- Vacuum leaks
- Head gasket leaks
- Damaged wiring of the spark plug in cylinder 7
- Faulty oil distributor
- Bad ignition coils
- Bad air-fuel ratio sensor
- Engine timing off
- Faulty fuel pressure sensor
- Faulty fuel injector
- Bad compression system
- Bad O2 sensor
- Contaminated fuel
- Bad fuel pump
- A damaged lifter or worn camshaft lobe
How to Diagnose the P0307 Trouble Code?
Follow the following steps to diagnose the P0307 engine code:
- Ensure the presence of the P0307 code by using an OBD-II scanner. Utilize the freeze frame data to check what’s going on. Perform a test drive after clearing the codes. If the P0307 code returns, move forward for further inspection.
- Test drive your car. If the codes return, then check other parts.
- Inspect the coil pack, wires, or spark plug on cylinder 7 to see if it is damaged or worn. Replace any of these parts if needed. You can try to move over the spark plug and ignition coil to another cylinder to see if you get a trouble code on the other cylinder instead – if so, replace the faulty spark plugs and ignition coil.
- Inspect the intake system for vacuum leaks.
- Inspect the ignition coil for cylinder number 7.
- Check the fuel injectors. If any of your fuel injectors are damaged, replace them.
- If your car has a distributor cap and ignition cables, inspect them and replace them if needed.
- Inspect the fuel pump and replace it if needed.
- Perform a compression test of cylinder 7 to check its compression system.
- Properly inspect the camshaft timing.
- Check the shaft or timing belt if needed.
- If all the above parts are working efficiently, and you are still getting the P0307 code, your PCM may be bad.
Common P0307 Code Diagnosis Mistakes
- Not switching the coils and spark plug to a different cylinder and rescanning to check if the misfire moves to another cylinder to see if the coil or spark plug is bad.
- Not properly inspecting all the parts.
- Not shifting the coil of cylinder 7 to a different cylinder to check if the misfire moves to another cylinder. This would show a bad coil.
- Replacing the unnecessary components.
- Not clearing the PCM codes after fixing the codes.
Repair Cost of P0307 Code
The repair cost of the P0307 code varies according to your vehicle model, labor cost, and the repair of the relevant part. To fix the P0307, your vehicle may need one or more below-given repairs:
| Parts | Cost |
| Spark Plug replacement | $60 to $260 |
| Fuel pump replacement | $250 to $1,090 |
| Spark plug wiring repair | $170 to $250 |
| Repair leaking head gasket | $1,400 to $3,100 |
| Ignition Coils | $220 to $650 |
| Fuel injector replacement | $1400 to $2000 |
What repairs can fix the P0307 Code?
One or more of the following repairs can fix the P0307 code:
- Replacing the bad fuel pump
- Replacing the bad spark plug in cylinder 7
- If your cylinder number 7 is damaged, repair or replace it
- Replacing the bad crankshaft sensor
- Replacing or fixing the head gasket leaks
- Replacing the damaged or corroded spark plug wires
- Replacing the bad or damaged fuel injectors
- Replacing the faulty camshaft sensor
- Replacing or repairing the damaged coil pack wires
- Replacing the bad EGR valve
- Replacing the bad O2 sensor
- Replacing the burned valves
- Replacing the bad MAF sensor
- Repairing the fuel rail leaks
- Repairing the vacuum leaks
- Replacing the damaged distributor cap
FAQ Section
How Serious is the P0307 Code?
The trouble code P0307 is considered a serious trouble code. Driving with an engine misfire is very hazardous, especially if your vehicle starts to stall in the middle of the road. If your engine starts stalling, it might be hard to get it started back up, leaving you in a dangerous condition.
Therefore, you must fix the P0307 trouble code immediately. The engine misfire may also badly damage the parts of the engine, which may lead your vehicle to an expensive repair.
Can a bad ignition coil cause P0307 code?
Yes, a bad ignition coil can cause the P0307 engine code. When the ignition coil goes bad, it doesn’t supply sufficient power to the spark plug to generate enough spark, causing engine misfiring.