P0300 on a 2017 Kia Sportage

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 2017 Kia Sportage

Ranked from 397 NHTSA owner complaints filed for this vehicle.

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1
Low cylinder compression from burnt valves / worn rings (Theta II oil-consumption defect)
High severity
Multiple owners had shop compression tests showing near-zero readings on one or more cylinders tied to burnt valves or worn piston rings from chronic oil burning - a direct and well-evidenced cause of persistent misfire on this engine.
Reported in 5 NHTSA complaints
2
Oil-fouled spark plugs / ignition coils (Theta II GDI oil consumption)
Medium severity
The well-documented Theta II 2.4L excessive oil consumption lets oil reach the combustion chamber and plug wells, fouling plugs and coils and causing intermittent misfires; several complaints explicitly describe oil-covered plugs alongside cylinder misfires.
Reported in 4 NHTSA complaints
Parts:spark plugs ignition coil
3
Faulty knock sensor or ignition coil circuit fault
Medium severity
Owners reported the car entering limp mode from a faulty knock sensor and rough running that persisted after plug/coil replacement, consistent with the KSDS-related electrical faults documented on this engine family.
Reported in 3 NHTSA complaints
Parts:knock sensor ignition coil
4
Worn spark plugs
Low severity
Standard misfire cause - worn or improperly gapped plugs cause weak spark, especially as the engine ages.
Common cause
Parts:spark plugs
5
Vacuum or intake leak
Medium severity
Unmetered air entering downstream of the throttle leans out one or more cylinders enough to misfire; check intake boots and PCV hoses for cracks.
Common cause
6
Clogged or leaking fuel injector
Medium severity
A partially clogged or dribbling injector starves or floods a cylinder, producing a repeatable misfire on that cylinder.
Common cause
Parts:fuel injector
7
EGR passage or valve fault
Low severity
Excess or uneven EGR flow at idle/light load can stall combustion in a cylinder and set a misfire code.
Common cause
Parts:EGR valve
8
Carbon buildup on intake valves
Low severity
Direct-injection engines lack fuel washing the intake valves, so carbon accumulates over time and can disrupt airflow/atomization enough to cause a misfire.
Common cause

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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

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.

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.

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.

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.

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 Rough Flashing Check Engine Light