P0300 on a 2013 Subaru Forester

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 2013 Subaru Forester

Ranked from 77 NHTSA owner complaints filed for this vehicle.

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1
Excessive Oil Consumption / Low Oil Level
High severity
The engine consumes oil at an abnormally high rate, leading to very low oil levels which can cause misfires, stalling, or catastrophic engine failure. Check oil level on the dipstick and monitor consumption between changes.
Reported in 12 NHTSA complaints
2
Catastrophic Engine Failure / Internal Damage
High severity
Often a result of oil starvation, internal components like rod bearings fail, causing knocking, stalling, and misfires. Look for metal shavings in the oil or a seized engine.
Reported in 4 NHTSA complaints
3
Blown Head Gasket
High severity
Coolant and oil mixing or loss of compression due to head gasket failure can cause misfires. Look for milky oil, oil in the coolant reservoir, or overheating.
Reported in 4 NHTSA complaints
4
Faulty Spark Plugs
Low severity
Worn or fouled spark plugs fail to ignite the air/fuel mixture properly. Inspect spark plugs for wear, carbon buildup, or oil fouling.
Common cause
5
Faulty Ignition Coils
Medium severity
A failing ignition coil will not provide sufficient voltage to the spark plug, causing a misfire. Test coil resistance or swap coils to see if the misfire moves.
Common cause
6
Vacuum Leak
Medium severity
Unmetered air entering the intake manifold leans out the air/fuel mixture, leading to random misfires. Check hoses and intake gaskets for leaks using a smoke tester.
Common cause
7
Clogged or Faulty Fuel Injectors
Medium severity
Poor fuel delivery prevents proper combustion. Check fuel pressure and perform an injector balance test.
Common cause

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