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P0300

P0300 on a 2019 Kia Sorento

P0300 is a generic OBD2 powertrain code for random or multiple cylinder misfire. Unlike P0301 through P0308, it does not point to one specific cylinder, so the cause can be ignition, fuel, air, sensor, or mechanical.

Not your vehicle? See general P0300 info.

Most common causes on the 2019 Kia Sorento

Ranked from 418 NHTSA owner complaints filed for this vehicle.

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  1. 1

    Low compression from rod-bearing wear / burnt valves (Theta II / Lambda II oil-consumption defect)

    High severity

    Multiple owners of this exact vehicle report cylinder misfires, burnt valves, detached head bolts, and rod-bearing wear tied to Kia's well-documented Theta/Lambda GDI oil-consumption defect, directly causing low compression and misfire.

    Reported in 6 NHTSA complaints
  2. 2

    Carbon-fouled valves from chronic oil burning

    Medium severity

    Heavy oil consumption documented across many complaints on this vehicle deposits carbon on valves and in the combustion chamber, which can disrupt sealing and trigger misfire.

    Reported in 2 NHTSA complaints
  3. 3

    Worn or fouled spark plugs / failing ignition coils

    Medium severity

    One owner had ignition coils and spark plugs replaced for cylinder-1/2 misfires tied to the oil-consumption condition; fouled plugs from oil-burning are a common secondary misfire cause here.

    Reported in 1 NHTSA complaint
    Parts:ignition coilspark plug
  4. 4

    Clogged or leaking fuel injectors

    Medium severity

    Deposits or a leaking injector unbalance the air/fuel ratio in one cylinder, producing a misfire.

    Common cause
    Parts:fuel injector
  5. 5

    Vacuum or intake leak

    Medium severity

    Unmetered air entering one cylinder's intake runner causes a lean misfire localized to that cylinder.

    Common cause
  6. 6

    EGR valve fault

    Low severity

    A stuck-open EGR valve dilutes the intake charge and can trigger a misfire, especially at idle.

    Common cause
    Parts:EGR valve

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0300 on your car still needs shop confirmation before any repair.

Common symptoms

  • Flashing or steady check engine light
  • Rough idle
  • Shaking under acceleration
  • Loss of power
  • Fuel smell from exhaust

What to check before replacing parts

1

Scan for cylinder-specific misfire codes

Look for: A companion P0301–P0308 pins the misfire to one cylinder — start there. P0300 with no cylinder code points at something hitting several at once: fuel pressure, a large vacuum leak, or timing.

2

Inspect the spark plugs and coils

Look for: Pull the plugs: black/sooty = rich, oily = oil intrusion, white/blistered = lean or overheating, cracked porcelain or an out-of-spec gap = replace. Then swap a coil to another cylinder — if a cylinder-specific code follows the coil, the coil is bad.

3

Check fuel trims for a vacuum leak

Look for: High positive short- and long-term trims (worst at idle, improving as RPM rises) mean unmetered air is getting in. Smoke-test the intake and listen for hissing.

4

Verify fuel pressure

Look for: Compare running/cranking pressure to the vehicle spec. Low or dropping pressure starves multiple cylinders and reads as a random misfire — suspect the pump, filter, or regulator.

5

Compression / leak-down test if ignition and fuel check out

Look for: A cylinder 15%+ below the others, or leak-down hissing from the intake (intake valve), exhaust (exhaust valve), or oil filler (rings), means the misfire is mechanical — not a swap-in part.

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Matching symptoms

Car Runs RoughFlashing Check Engine Light