P0307 – Cylinder 7 Misfire Detected (OBD2)
P0307 means "Cylinder 7 Misfire Detected". A misfire means that the fuel in a cylinder did not burn properly; the engine control unit detects it from tiny changes in crankshaft speed.
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P0307 quick summary
| Fault code | P0307 |
|---|---|
| Meaning | Cylinder 7 Misfire Detected |
| System | Powertrain (Engine & Transmission) |
| Vehicles | Generic OBD2 |
| Severity | High |
| Can I drive? | Only gently and for short distances. If the engine shakes heavily or the Check Engine light flashes, stop as soon as it is safe – unburnt fuel can overheat and destroy the catalytic converter. |
| Repair cost | €20 – €1,500 |
How misfire detection works
Every time a cylinder fires, it accelerates the crankshaft slightly. The engine control unit watches the crankshaft position sensor signal and measures these accelerations for each cylinder. If one cylinder contributes less than expected, it counts a misfire. Above a certain rate the Check Engine light comes on; if the rate is high enough to damage the catalytic converter, the light flashes and some engines switch off fuel to that cylinder (P0363).
Codes P0301 to P0312 name the cylinder that misfires; P0300 means several cylinders or a random pattern. Related codes cover misfires detected with low fuel level (fuel starvation), during the first 1,000 revolutions after starting, or a single misfiring cylinder that could not be identified.
A misfire always has one of three root causes: no or weak spark, wrong amount of fuel, or poor compression. On petrol engines, ignition coils and spark plugs are by far the most frequent culprits. On diesels, injectors and compression are the usual suspects. Continuing to drive with heavy misfires sends unburnt fuel into the exhaust and can destroy the catalytic converter within a short time.
The code refers to cylinder 7. Cylinder numbering differs between manufacturers (and between banks on V engines), so check the numbering for your engine in the service information before replacing parts.
On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16691 (P0307). Both numbers mean the same fault.
Symptoms of P0307
- Engine shakes or stutters, especially at idle or under load
- Flashing or steady Check Engine light
- Loss of power and poor acceleration
- Higher fuel consumption, smell of fuel from the exhaust
- Hard starting or rough cold start
Most common causes of P0307 (most likely first)
Mechanic's Pro Tip
The swap test is the cheapest diagnosis there is. Move the coil from the misfiring cylinder to another one, clear the codes and drive: if the misfire code moves to the new cylinder (for example from P0302 to P0303), you have found a faulty coil without buying any parts.
1.Faulty ignition coil
Most likelyThe most common cause on modern petrol engines with one coil per cylinder.
2.Worn or fouled spark plugs
Worn electrodes, the wrong plug type or oil fouling cause weak sparks, especially under load.
3.Injector problem
A clogged, leaking or electrically faulty injector delivers the wrong amount of fuel.
4.Vacuum leak or low fuel pressure
Affects several cylinders at once and often sets lean codes as well.
5.Low compression
Burnt valves, worn piston rings, a damaged head gasket or a jumped timing chain/belt.
Step-by-step diagnostic guide
- 1
Read codes and misfire counters
Read all codes and look at the misfire counters per cylinder in live data. Note when the misfire occurs – cold, warm, idle, under load – and check for related lean, injector or coil codes.
- 2
Inspect spark plugs
Remove and inspect the plugs: worn electrodes, cracked insulators, oil or carbon fouling. Replace them if they are due or damaged.
- 3
Swap coil and plug between cylinders
Swap the ignition coil of the misfiring cylinder with a neighbour and clear the codes. If the misfire moves with the coil, replace the coil. Repeat with the spark plug and, on engines where it is easy, the injector.
- 4
Check fuel and air
Check fuel trims, look for vacuum leaks with a smoke test and test injector operation (sound, resistance, balance test).
- 5
Compression or leak-down test
If the misfire stays with the cylinder after swapping parts, do a compression or leak-down test to check valves, rings and head gasket.
Multimeter: Compression should be within about 10–15 % between cylinders; a cylinder far below the others has a mechanical problem.
Frequently asked questions
Can I keep driving with P0307?
Only gently and for short distances. If the engine shakes heavily or the Check Engine light flashes, stop as soon as it is safe – unburnt fuel can overheat and destroy the catalytic converter.
How much does it cost to fix P0307?
Typical repair costs are 20 € – 1500 €, depending on the cause and the vehicle. The most common fixes are: faulty ignition coil; worn or fouled spark plugs; injector problem. Always confirm the cause with the tests above before buying parts.
Can a misfire damage my engine?
The bigger risk is the catalytic converter, which overheats from unburnt fuel. A misfire caused by low compression or a jumped timing chain can also indicate serious engine damage, so do not ignore it.
Should I replace all ignition coils at once?
Only if they are old and one has already failed – the others often follow. Otherwise replacing just the faulty coil found with the swap test is fine.
What is the difference between P0307 and similar codes?
P0307 belongs to a group of codes for the same component that differ in the type or location of the fault: P0304 – Cylinder 4 Misfire Detected; P0305 – Cylinder 5 Misfire Detected; P0306 – Cylinder 6 Misfire Detected; P0308 – Cylinder 8 Misfire Detected; P0309 – Cylinder 9 Misfire Detected; P0310 – Cylinder 10 Misfire Detected. The tests on this page apply to the whole group; the type of fault tells you where to start.
Related fault codes
This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.