P0300 on a 2016 Chevrolet Impala Eco Eassist
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 Chevrolet Impala Eco Eassist
Ranked from 786 NHTSA owner complaints filed for this vehicle.
- 1
Cracked piston / low compression
High severityA complaint documents a confirmed cylinder-1 misfire traced by a mechanic to a cracked piston and described as a known issue for this model-year engine; a second complaint on the same engine family logged a P0302 cylinder-2 misfire ultimately attributed to the pistons.
Reported in 2 NHTSA complaints - 2
Head gasket failure allowing oil to foul cylinders
Medium severityA complaint describes the main head gasket failing on these vehicles and leaking oil; a compromised gasket can also let combustion-sealing and cylinder compression suffer, contributing to rough-running or misfire symptoms.
Reported in 1 NHTSA complaintParts:head gasket - 3
Worn spark plugs or a failing ignition coil
Medium severityDegraded plugs or a weakening coil cause an intermittent spark-side misfire, usually worse under load or acceleration.
Common cause - 4
Clogged or leaking fuel injector
Medium severityA fouled or leaking injector delivers an uneven fuel charge to one cylinder, producing a repeatable misfire on that cylinder.
Common causeParts:fuel injector - 5
Vacuum or intake leak
Medium severityUnmetered air entering after the MAF leans one or more cylinders enough to misfire, especially at idle.
Common cause - 6
Carbon-fouled intake valves
Medium severityDirect-injection engines accumulate intake-valve deposits over time that disturb airflow and combustion at one or more cylinders.
Common cause - 7
EGR valve fault
Low severityExcess or uneven exhaust gas recirculation can dilute the charge in a cylinder enough to misfire, particularly at idle or light cruise.
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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