Worn or faulty spark plug, spark plug wire, distributor cap and rotor where fitted. Faulty ignition coil (coil pack) on cylinder 7. Vacuum leak (listed by RepairPal). Low or weak fuel pressure, or running out of fuel. Improperly working EGR system (listed by RepairPal). Incorrect ignition timing or a defective MAF, crankshaft, camshaft or throttle position sensor (listed by RepairPal). Mechanical engine problems such as poor compression, a burned exhaust valve, a leaking head gasket or other valve problems. Faulty fuel injector or oxygen sensor (listed by OBD-Codes.com; RepairPal calls both common misdiagnoses). Faulty catalytic converter or a defective engine computer (listed by OBD-Codes.com only).

Replace the spark plug, plug wire or boot, or distributor cap and rotor where fitted. Replace the cylinder 7 ignition coil if testing or a swap shows it's at fault. Repair vacuum leaks or intake manifold gasket leaks. Repair fuel delivery problems (weak pump, clogged filter) once testing confirms them. Repair EGR faults, ignition timing or sensor faults found during diagnosis. Repair mechanical problems (valves, rings, head gasket) found by a compression or leak-down test.

P0307⚡ Ignition / engine misfireStop and fix promptly

P0307: Cylinder 7 Misfire Detected (Meaning, Causes, Fixes)

Q: What does P0307 mean?

P0307 means the engine computer has detected that cylinder 7 isn't firing properly. Worn or faulty ignition parts (spark plug, plug wire, coil) are the most common cause, but vacuum leaks, low fuel pressure, EGR faults, sensor faults and mechanical engine problems can also set it. P0307 is a generic OBD-II code, so it applies to all OBD-II vehicles, though repair steps vary by make and model. RepairPal explains that the misfire monitor counts crankshaft sensor pulses, and when cylinder 7 isn't contributing its share (more than about a 2 percent RPM variance between cylinders) it sets P0307; above about 10 percent the check engine light blinks to warn of a misfire harmful to the catalytic converter. Cylinder 7 only exists on engines with seven or more cylinders, so in practice this is a V8, V10 or V12 code; the forum threads on OBD-Codes.com are mostly Ford, Chevrolet/GMC, Dodge/Ram and Jeep V8 and V10 trucks, vans and SUVs. Cylinder numbering differs between engines, so check your service information to find cylinder 7. The sources disagree on several causes: OBD-Codes.com lists faulty oxygen sensors and fuel injectors, while RepairPal calls fuel injectors and oxygen sensors common misdiagnoses for P0307. OBD-Codes.com also lists a burned exhaust valve, a faulty catalytic converter, running out of fuel and a defective computer, while RepairPal adds incorrect ignition timing, vacuum leaks, low fuel pressure, EGR faults and MAF, crank/cam and throttle position sensor faults.

Q: Can I keep driving with P0307?

Stop and fix promptly. RepairPal rates P0307 'Urgent', meaning a malfunction that can cause severe damage to the vehicle. OBD-Codes.com's P0307 page gives no severity rating and suggests that if there are no symptoms you can clear the code and see whether it comes back. Treat it as serious: RepairPal explains that a flashing check engine light means a misfire bad enough to harm the catalytic converter. If the light is flashing, ease off, avoid hard acceleration and get it checked as soon as you safely can.

Reviewed 2026-10-24 · Based on 2 cited source(s)

What P0307 means

P0307 is a generic OBD-II code, so it applies to all OBD-II vehicles, though repair steps vary by make and model. RepairPal explains that the misfire monitor counts crankshaft sensor pulses, and when cylinder 7 isn't contributing its share (more than about a 2 percent RPM variance between cylinders) it sets P0307; above about 10 percent the check engine light blinks to warn of a misfire harmful to the catalytic converter. Cylinder 7 only exists on engines with seven or more cylinders, so in practice this is a V8, V10 or V12 code; the forum threads on OBD-Codes.com are mostly Ford, Chevrolet/GMC, Dodge/Ram and Jeep V8 and V10 trucks, vans and SUVs. Cylinder numbering differs between engines, so check your service information to find cylinder 7. The sources disagree on several causes: OBD-Codes.com lists faulty oxygen sensors and fuel injectors, while RepairPal calls fuel injectors and oxygen sensors common misdiagnoses for P0307. OBD-Codes.com also lists a burned exhaust valve, a faulty catalytic converter, running out of fuel and a defective computer, while RepairPal adds incorrect ignition timing, vacuum leaks, low fuel pressure, EGR faults and MAF, crank/cam and throttle position sensor faults.

Severity: can I keep driving?

Stop and fix promptly

RepairPal rates P0307 'Urgent', meaning a malfunction that can cause severe damage to the vehicle. OBD-Codes.com's P0307 page gives no severity rating and suggests that if there are no symptoms you can clear the code and see whether it comes back. Treat it as serious: RepairPal explains that a flashing check engine light means a misfire bad enough to harm the catalytic converter. If the light is flashing, ease off, avoid hard acceleration and get it checked as soon as you safely can.

Common symptoms

Check engine light on, or flashing while the misfire is happening
Rough running, stumbling, hesitation or jerking when accelerating
Engine harder to start (listed by OBD-Codes.com)
Dying at stop signs, rough idle, lack of power or lower fuel economy (listed by RepairPal)
Often no adverse symptoms noticed by the driver (noted by RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Worn or faulty spark plug, spark plug wire, distributor cap and rotor where fitted
Faulty ignition coil (coil pack) on cylinder 7
Vacuum leak (listed by RepairPal)
Low or weak fuel pressure, or running out of fuel
Improperly working EGR system (listed by RepairPal)
Incorrect ignition timing or a defective MAF, crankshaft, camshaft or throttle position sensor (listed by RepairPal)
Mechanical engine problems such as poor compression, a burned exhaust valve, a leaking head gasket or other valve problems
Faulty fuel injector or oxygen sensor (listed by OBD-Codes.com; RepairPal calls both common misdiagnoses)
Faulty catalytic converter or a defective engine computer (listed by OBD-Codes.com only)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes and freeze frame data and write them down. RepairPal says to note the engine load, throttle position, RPM and road speed when the code set, so you can recreate the conditions on a test drive.
If other codes are stored (lean, fuel, EGR or sensor codes), look at those too, since RepairPal notes the misfire may come from another system's fault.
With the engine off and cool, check the wiring and connectors to cylinder 7 and inspect its coil, spark plug and plug wire or boot for wear, arcing or heat damage. RepairPal says a healthy plug tip is sandy colored, not sooty black, white or greenish.
If the spark plugs and wires are due by your maintenance schedule, OBD-Codes.com suggests replacing them as a first step.
If your scan tool shows a per-cylinder misfire counter, watch cylinder 7. If not, RepairPal suggests swapping the coil or plug with another cylinder, clearing the codes and seeing whether the misfire moves.
With the engine running, listen for a vacuum leak (a hiss) around the intake.

Typical fixes

Replace the spark plug, plug wire or boot, or distributor cap and rotor where fitted
Replace the cylinder 7 ignition coil if testing or a swap shows it's at fault
Repair vacuum leaks or intake manifold gasket leaks
Repair fuel delivery problems (weak pump, clogged filter) once testing confirms them
Repair EGR faults, ignition timing or sensor faults found during diagnosis
Repair mechanical problems (valves, rings, head gasket) found by a compression or leak-down test

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The check engine light is flashing
The misfire stays on cylinder 7 after replacing the plug and coil
You smell rotten eggs from the exhaust, which OBD-Codes.com says can mean the catalytic converter needs replacing
A compression or leak-down test is needed to check valves, rings or the head gasket
Fuel trim, fuel pressure or ignition scope testing is needed to find a lean or ignition misfire

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0307?

RepairPal rates it 'Urgent'. A misfire can damage the catalytic converter, so limit driving, especially if the check engine light is flashing, and get it fixed soon.

Is P0307 always a bad coil or spark plug?

No. Ignition parts are a common cause, but vacuum leaks, low fuel pressure, EGR faults, sensors and mechanical problems like low compression or a burned valve can also cause it. Swapping the coil or plug to another cylinder is a cheap way to see if the misfire follows the part.

What's the difference between P0300 and P0307?

P0307 pins the misfire to cylinder 7. P0300 means random or multiple cylinders are misfiring, which usually points to something shared by all cylinders, such as fuel pressure or a vacuum leak.

Sources

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.