EngineLightCodes
Powertrain code

P0300 Random/Multiple Cylinder Misfire Detected

Severity
Stop soon
Typical repair cost
$30–$1,650
Do it yourself
Possible, medium
Shop time
0.5–6 hours

The engine is misfiring on more than one cylinder, or the computer can't tell which one. Because several cylinders are affected, look for something they all share: a vacuum leak, low fuel pressure, worn plugs or bad fuel.

How the engine computer detects it

The engine module detects misfire from crankshaft speed: a cylinder that does not fire gives no acceleration impulse. At a catalyst-damaging rate (CARB: at least 5 % per 200 revolutions) the warning light flashes; at an emissions-relevant rate (at least 1 % per 1,000 revolutions – GM about 2–5 %, Ford 0.9–1.5 %) it comes on after two trips. Ford and GM may shut off a misfiring cylinder's injector to protect the catalyst. P0300 sets when the misfire cannot be assigned to one cylinder: several cylinders each account for more than 10 %, the cylinder changes randomly, or – at Ford – the cylinder cannot be identified at high speed. It often appears together with cylinder codes. Causes are usually systemic: false air, worn plugs on several cylinders, fuel pressure or fuel quality, valve timing – and false detection from a damaged tone wheel, rough roads or vibration. Bulletins name coils, cracked plug insulators and wrong plug gaps.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

  • Check engine light on, flashing at a catalyst-damaging rate
  • Rough idle, jerking, vibration
  • Loss of power, hesitation
  • Smell of unburnt fuel, higher consumption

Common causes

  1. False air (vacuum leak, crankcase ventilation, intake gasket) Most likely
  2. Worn or wrong spark plugs on several cylinders, faulty ignition coils Most likely
  3. Fuel pressure too low or high, contaminated fuel Possible
  4. Valve timing (stretched chain), valves, compression on several cylinders Less likely
  5. False detection: tone wheel or pulley, rough road, vibration, software Less likely

How to diagnose P0300

  1. Check for other codes. Cylinder-specific misfires (P0301 to P0308) or lean codes (P0171, P0174) point to where to look first.
  2. Listen for hissing at idle and inspect vacuum hoses, the intake boot and the PCV hose for cracks.
  3. Check the spark plugs. If they are past their service interval, replace the whole set.
  4. Have fuel pressure measured. A weak pump or clogged filter starves every cylinder at once.
  5. If it only misfires on rough roads or at one speed, ask a shop to check the crankshaft sensor and its reluctor ring.

Vehicles that report P0300 most

VehicleYearsReportsMedian miles
Ford Escape2014–20243641k
Chevrolet Silverado 15002009–20232174k
Ford Fusion2014–201919100k
Honda Accord2011–20241446k
Ford Edge2016–201814—
Kia Soul2012–202114—
Chevrolet Tahoe2007–202612120k
Honda CR-V2000–20191164k
GMC Sierra 15002011–20221181k
Ford F-1502011–20221012k

Counts of owner complaints to the NHTSA that mention P0300 (465 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.

Reading the code

P
Powertrain
0
Generic (SAE) code
3
Ignition system or misfire
00
Specific fault

Questions drivers ask

Can I drive with code P0300?

If the check engine light is flashing, stop driving: the misfire is bad enough to overheat and ruin the catalytic converter. With a steady light, drive gently and only as far as you need to.

Will my car pass an emissions inspection with P0300?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0300 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0300 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.

Often reported together

Codes that owners mention in the same NHTSA complaints as P0300. They can point to a shared cause, so it's worth checking them together.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.