P0300
Random/Multiple Cylinder Misfire Detected
The engine computer has detected misfires in one or more cylinders, but not limited to a single cylinder. This usually means the engine is not burning fuel correctly because of bad ignition parts, fuel delivery problems, air leaks, sensor faults, or internal engine issues.
- SEV
- 4/5
- DRIVE
- CAUTION
- DIY
- $20–$300
- SHOP
- $120–$1,500
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Worn or fouled spark plugs
- Faulty ignition coils, wires, distributor cap, or rotor where equipped
- Vacuum leak or unmetered air entering the engine
Typical repair cost
DIY usually runs $20–$300. Typical shop repair lands around $120–$1,500, depending on the root cause.
01 / Definition
P0300 means the powertrain control module has detected random or multiple cylinder misfires. Because the misfire is not isolated to one cylinder, diagnosis usually involves checking ignition, fuel, air metering, vacuum leaks, and mechanical engine condition. The code may appear with other misfire codes, fuel trim codes, or sensor-related codes that help identify the root cause.
02 / Drive status
With caution. You may be able to drive short distances, but the engine may run poorly, stall, or lose power. Continued driving can damage the catalytic converter and may make the vehicle unsafe in traffic.
03 / Symptoms
- Rough idle
- Engine hesitation or stumbling
- Loss of power
- Poor acceleration
- Check engine light on
- Poor fuel economy
- Shaking or vibration while driving
- Hard starting
- Stalling
- Strong fuel smell from exhaust
04 / Causes
| 1 | Worn or fouled spark plugs | high |
|---|---|---|
| 2 | Faulty ignition coils, wires, distributor cap, or rotor where equipped | high |
| 3 | Vacuum leak or unmetered air entering the engine | high |
| 4 | Low or weak fuel pressure from pump, filter, or pressure regulator problems | high |
| 5 | Defective mass airflow sensor causing incorrect air measurement | medium |
| 6 | Incorrect ignition timing or cam/crank sensor problem | medium |
| 7 | Improperly functioning EGR system | medium |
| 8 | Defective throttle position sensor or throttle body issue | medium |
| 9 | Mechanical engine problems such as low compression, valve issues, or head gasket leaks | low |
05 / Diagnostic sequence
- 01Scan for stored and pending codes, including misfire, fuel trim, MAF, O2, crankshaft, camshaft, and EGR codes.
- 02Check freeze frame data to see engine load, temperature, RPM, and fuel trim when the misfire happened.
- 03Inspect spark plugs, ignition coils, plug wires, distributor cap, and rotor if equipped.
- 04Look for vacuum leaks, loose hoses, cracked intake boots, and intake manifold leaks.
- 05Check fuel pressure and fuel volume against manufacturer specifications.
- 06Inspect the air intake system and clean or test the MAF sensor if needed.
- 07Verify crankshaft and camshaft sensor signals and check ignition timing data if the vehicle supports it.
- 08Test EGR and throttle body operation if symptoms point to airflow or idle control issues.
- 09Perform a compression test and leak-down test if ignition and fuel checks do not find the problem.
06 / Repairs
| 1 | Replace worn spark plugs and any damaged ignition wires or coils. | $20–$400 |
|---|---|---|
| 2 | Repair vacuum leaks, loose intake connections, or damaged hoses. | $10–$250 |
| 3 | Restore proper fuel pressure by replacing a clogged filter, weak pump, or faulty regulator. | $50–$900 |
| 4 | Clean or replace a faulty MAF sensor, and service the throttle body if needed. | $15–$250 |
| 5 | Repair faulty crankshaft, camshaft, EGR, or ignition timing-related components. | $50–$700 |
| 6 | Repair internal engine problems such as valve damage, head gasket leaks, or low compression. | $500–$3,000+ |
MFG / Manufacturer notes
These supplements add make-specific diagnostic framing. Pages without full matrix backing or lane approval stay guarded and canonicalize back here until they are explicitly approved for indexing.
07 / Related codes
08 / FAQ
What does P0300 mean?
It means the engine computer detected random or multiple cylinder misfires.
Can a bad spark plug cause P0300?
Yes. Worn or fouled spark plugs are one of the most common causes.
Will P0300 clear itself?
It may clear temporarily if the problem goes away, but it will usually return until the cause is fixed.
Can I keep driving with P0300?
Only for short distances with caution. If the engine is shaking badly, stalling, or flashing the check engine light, stop driving and diagnose it right away.
Does P0300 always mean the ignition system is bad?
No. It can also be caused by vacuum leaks, fuel pressure problems, sensor faults, or engine mechanical problems.
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.