P0300
Random or Multiple Cylinder Misfire
Quick answer: P0300 means random or Multiple Cylinder Misfire. Fixing the underlying cause typically runs $195 to $1,550 at an independent shop. Get it checked promptly.
- Severity
- High
- Safe to drive?
- Get it checked promptly
- Typical repair
- $195 to $1,550
- Most likely cause
- Worn spark plugs or failing ignition coils across several cylinders (by far the most common, especially past 60,000 to 100,000 miles on the original plugs)
What P0300 means
The engine computer watches how evenly the crankshaft speeds up on each power stroke. When several cylinders stumble, or the misfires jump around instead of staying on one cylinder, it logs P0300 rather than a cylinder-specific code. The random pattern is the clue: the cause is usually something shared by the whole engine (spark, fuel pressure, air, or compression) instead of one bad part on one cylinder.
Common symptoms
What drivers usually notice with this code.
- Check-engine light flashing under acceleration, or steady at idle
- Engine shakes or stumbles, most noticeable at idle or a stoplight
- Hesitation and loss of power when you press the gas
- Noticeably worse fuel economy
- Hard starting, or the engine cranks longer than usual
Common causes
Ranked from most to least likely.
- 1Worn spark plugs or failing ignition coils across several cylinders (by far the most common, especially past 60,000 to 100,000 miles on the original plugs)
- 2A vacuum leak letting unmetered air into the intake (cracked hose, PCV line, or leaking intake manifold gasket)
- 3Weak fuel delivery: a failing fuel pump, clogged fuel filter, or dirty injectors starving every cylinder at once
- 4A bad tank of fuel, water in the fuel, or the wrong octane
- 5A failing EGR valve stuck open, flooding the intake with exhaust gas at idle
- 6Low compression from worn rings or a stretched timing chain or belt (the expensive end, and usually paired with high mileage)
Can I keep driving?
If the light is flashing, stop driving and get it towed, because an active misfire dumps raw fuel into the exhaust and can destroy a catalytic converter in minutes; if the light is steady, drive gently straight to a shop.
Severity: High. A flashing check-engine light always means stop, whatever the code says.
Ballpark cost
What P0300 usually costs to fix
A range, not a quote. What you pay depends on your vehicle, your area, and which of the causes above turns out to be the real one.
Typical parts and labor at an independent shop. Dealer rates run higher.
That spread is wide on purpose. P0300 points at a system, not a single part, so the real answer depends on what the diagnosis finds. Use the range to know what to expect. If an estimate comes in higher, it usually means the specific repair is more involved, and it is always fair to ask what is included.
Next steps
What to do next
Start with the cheap and likely fix: if the plugs and coils are anywhere near their service interval, replace the full set rather than chasing one. If new ignition parts do not solve it, a shop should smoke-test for vacuum leaks and check fuel pressure before anyone looks at internal engine work. A compression test is the check that separates a simple tune-up from a rebuild, so it is worth confirming before any major engine repair.
Walk in informed
Ask for the diagnosis in writing and which test confirmed it, so you understand exactly what is being fixed. Fixxr shows you what the job typically costs near you, so you can approve the work with confidence.
Sources & further reading
- NHTSA — Check for vehicle safety recalls — look up open recalls for your vehicle by VIN, free
- FTC — Auto repair basics — your consumer rights at the repair shop
- AAA — Car repair and maintenance costs — independent guidance on what repairs should cost
Cost ranges and guidance reviewed July 2026.
Keep exploring
What the repair costs
Related symptoms
P0300 FAQ
P0300 questions, answered
Can I drive with a P0300 code?
If the light is flashing, stop driving and get it towed, because an active misfire dumps raw fuel into the exhaust and can destroy a catalytic converter in minutes; if the light is steady, drive gently straight to a shop.What does the P0300 code mean?
The engine computer watches how evenly the crankshaft speeds up on each power stroke. When several cylinders stumble, or the misfires jump around instead of staying on one cylinder, it logs P0300 rather than a cylinder-specific code. The random pattern is the clue: the cause is usually something shared by the whole engine (spark, fuel pressure, air, or compression) instead of one bad part on one cylinder.What are the most common causes of a P0300 code?
The most likely causes, roughly in order, are worn spark plugs or failing ignition coils across several cylinders (by far the most common, especially past 60,000 to 100,000 miles on the original plugs); a vacuum leak letting unmetered air into the intake (cracked hose, PCV line, or leaking intake manifold gasket); weak fuel delivery: a failing fuel pump, clogged fuel filter, or dirty injectors starving every cylinder at once; a bad tank of fuel, water in the fuel, or the wrong octane. Start with the cheap and likely fix: if the plugs and coils are anywhere near their service interval, replace the full set rather than chasing one. If new ignition parts do not solve it, a shop should smoke-test for vacuum leaks and check fuel pressure before anyone looks at internal engine work. A compression test is the check that separates a simple tune-up from a rebuild, so it is worth confirming before any major engine repair.How much does it cost to fix a P0300 code?
Fixing the underlying problem behind a P0300 code typically runs $195 to $1,550 at an independent shop, including parts and labor. The exact figure depends on your vehicle and which part turns out to be at fault.
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