Misfires
P0300
Random / Multiple Cylinder Misfire Detected
What does P0300 mean?
P0300 means the engine computer detected misfires that are not confined to one cylinder. A misfire is a combustion event that failed or burned incompletely. Because the fault moves between cylinders rather than staying in one, the cause is usually something all the cylinders share, such as fuel, spark or air.
Can I keep driving with P0300?
High urgency
A steady light means get it looked at soon; a FLASHING light means an active misfire is dumping raw fuel into the exhaust and can destroy the catalytic converter — stop driving.
Symptoms of P0300
Rough or shaky idle
Hesitation or stumbling under acceleration
Flashing check engine light — stop driving if it is flashing
Noticeably worse fuel economy
Common causes of P0300
Worn spark plugs or ignition coils
A vacuum leak letting unmetered air into the intake
Low fuel pressure or clogged fuel injectors
A failing mass airflow sensor skewing the mixture
These are ordered roughly by how often they turn out to be the cause — but the code names a system, not a part. Confirming which one is yours takes data from the running engine.
What does it cost to fix P0300?
$100 – $1,000
Typical US independent-shop range, parts and labour included. It is wide on purpose: the cheap end is usually a sensor, a hose or a cap, and the expensive end is the major component the code was reporting on. Which one you need is a diagnosis, not a guess — and dealer rates run higher than these figures.
Do not guess on P0300
This page explains the code. It cannot tell you which cylinder, coil, or injector is yours — and with a misfire, guessing wrong gets expensive fast. Kaiju Mechanic reads what your car is actually reporting, plus live sensor data through any standard ELM327 adapter, and interprets it against your exact year, make, model and mileage. You can also just ask it about P0300 in chat — no adapter needed for that.
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