P0300 on a 2020 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 2020 Kia Soul
Ranked from 364 NHTSA owner complaints filed for this vehicle.
- 1
Chronic oil consumption leading to low oil level and oil-starvation-related misfire
High severityA very large share of these complaints describe burning 1+ quart of oil per 1,000 miles with no low-oil warning, which starves lubrication and precedes stalling/misfire events.
Reported in 11 NHTSA complaints - 2
Worn/defective piston rings (Kia recall SC209/21V259) causing low compression and cylinder misfire
High severityThis engine has a documented piston-ring manufacturing defect (subject of recall SC209) that drives oil consumption and, per these complaints, connecting-rod bearing failure and piston vibration/knock consistent with compression-loss misfire.
Reported in 5 NHTSA complaints - 3
Camshaft/CVVT actuator or timing failure disrupting valve timing
High severityComplaints report a broken CVVT pin, a camshaft position sensor circuit code, and camshaft/timing that 'were not operating properly,' all of which desynchronize valve events and produce misfire.
Reported in 4 NHTSA complaints - 4
Metal debris in oil from bearing/ring wear damaging cylinders
High severityTwo complaints specifically document metal shavings found in the oil, consistent with internal wear products circulating and further damaging cylinders/bearings.
Reported in 2 NHTSA complaints - 5
Worn or fouled spark plugs
Medium severityDegraded plug gaps or carbon fouling weaken spark, especially under load, producing random misfire.
Common causeParts:spark plugs - 6
Failing ignition coil(s)
Medium severityA weakening coil-on-plug unit drops spark energy to one cylinder, causing a repeating single- or multi-cylinder misfire.
Common causeParts:ignition coil - 7
Vacuum or intake air leak
Medium severityUnmetered air entering after the MAF throws off the air/fuel ratio enough to misfire under some conditions.
Common cause - 8
EGR valve fault
Low severityA stuck-open EGR valve introduces too much exhaust gas at idle/low load, destabilizing combustion.
Common causeParts: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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