Ask Andy AIP0300 Random/Multiple Cylinder Misfire Detected
What it means, what causes it, and what it costs to fix.
What P0300 means
The engine computer sees misfires on more than one cylinder, or moving between cylinders. Because it isn't one cylinder, the cause is usually something every cylinder shares: fuel pressure, a vacuum leak, the airflow sensor, or worn plugs all around.
Can I drive with P0300?
Severity: High. Fix right away. It can cause damage or leave you stranded.
Limit driving. A flashing check engine light means stop. Ongoing misfires can overheat the catalytic converter and turn a cheap fix into an expensive one.
Get a diagnosis for your exact car
Tell Andy your year, make, model, and symptoms. You'll get best case, most likely, and worst case, with parts and labor costs. Free, in about 15 seconds.
Ask Andy about P0300Symptoms
- Rough idle and shaking
- Hesitation or bucking on acceleration
- Flashing or steady check engine light
- Poor fuel economy
- Hard starting
Common causes
Most likely first.
- Worn spark plugs across the engine
- Vacuum leak (cracked hose, intake gasket, PCV valve)
- Low fuel pressure: weak pump or clogged filter
- Dirty or failing mass airflow (MAF) sensor
- Bad gas or water in the fuel
- Timing chain or belt stretched or jumped a tooth
How to diagnose P0300
- Check misfire counters in live data to see which cylinders are actually missing.
- Look for lean codes (P0171/P0174). Together with P0300 they strongly suggest a vacuum leak or fuel delivery issue.
- Inspect plugs and coils, and smoke-test the intake for vacuum leaks.
- Test fuel pressure against spec.
- If cam/crank correlation codes (P0016) are present, check timing.
Tip: most US auto parts stores will read your codes for free.
Repair costs
| Full set of spark plugs | $100–$400 installed |
| Vacuum leak / PCV repair | $50–$400 |
| MAF sensor cleaning or replacement | $10 cleaner to $350 installed |
| Fuel pump | $400–$1,200 installed |
Typical US prices. Your vehicle, region, and shop rates will change these.
P0300 FAQ
What does P0300 mean?
P0300 means "Random/Multiple Cylinder Misfire Detected." The engine computer sees misfires on more than one cylinder, or moving between cylinders. Because it isn't one cylinder, the cause is usually something every cylinder shares: fuel pressure, a vacuum leak, the airflow sensor, or worn plugs all around.
Can I drive with a P0300 code?
Limit driving. A flashing check engine light means stop. Ongoing misfires can overheat the catalytic converter and turn a cheap fix into an expensive one.
What is the most common cause of P0300?
The most common cause is: Worn spark plugs across the engine. Other causes include vacuum leak and low fuel pressure: weak pump or clogged filter.
How much does it cost to fix P0300?
Typical repairs run about $10 to $1,200 in the US, depending on the cause. Full set of spark plugs: $100–$400 installed.
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