P0300 on a 2016 Kia Soul

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 2016 Kia Soul

Ranked from 802 NHTSA owner complaints filed for this vehicle.

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1
Low compression from rod-bearing wear or piston/ring damage (Nu/Gamma GDI internal engine failure)
High severity
A very large share of this vehicle's complaints describe rod-bearing knock (P1326), a defective #4 connecting rod, a blown piston, and damaged piston rings — all part of the well-documented Kia/Hyundai GDI engine internal-failure pattern (subject of the Hyundai/Kia engine settlement) that destroys cylinder compression and causes misfires.
Reported in 7 NHTSA complaints
2
Oil-fouled spark plugs from excessive oil consumption
High severity
Multiple owners reported the engine burning oil rapidly enough to run the level to zero between changes, including oil found leaking near the spark plugs during a head-gasket repair — oil fouling on the plugs directly causes misfires.
Reported in 5 NHTSA complaints
Parts:spark plugs
3
Catalytic converter melting/clogging (NHTSA recall 19V120 / Kia SC176)
High severity
Several owners had the catalytic converter melt or clog under the documented overheating recall, creating severe exhaust backpressure that caused stalling and loss-of-power symptoms alongside misfire-adjacent rough running.
Reported in 5 NHTSA complaints
Parts:catalytic converter
4
Knock sensor fault / P1326 recall repair not holding
Medium severity
One owner had the knock sensor replaced under the P1326 recall and the code returned within six miles, indicating the underlying rod/engine condition (not just the sensor) was still driving the fault.
Reported in 1 NHTSA complaint
Parts:knock sensor
5
Worn or fouled spark plugs (general wear)
Medium severity
Standard high-mileage plug wear or gap erosion weakens spark independent of the oil-consumption pattern above.
Common cause
Parts:spark plugs
6
Failing ignition coil(s)
Medium severity
A cracked boot or internal coil breakdown drops spark energy to a cylinder, especially under load.
Common cause
Parts:ignition coil
7
Vacuum or intake air leak
Medium severity
Unmetered air leans out one or more cylinders, producing an intermittent misfire.
Common cause
8
EGR valve fault
Low severity
A stuck or leaking EGR valve dilutes the intake charge unpredictably and can trigger a misfire.
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

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