P0300 on a 2017 Hyundai Elantra

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 Hyundai Elantra

Ranked from 759 NHTSA owner complaints filed for this vehicle.

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1
Excessive Internal Oil Consumption / Piston Ring Failure
High severity
Defective piston rings or internal engine wear causes rapid oil burning, leading to low oil levels, misfires, knocking, and catastrophic engine failure.
Reported in 9 NHTSA complaints
2
Timing Chain/Tensioner Failure due to Oil Starvation
High severity
Excessive internal oil consumption starves the hydraulic timing chain tensioner, causing the chain to jump time or loosen, leading to severe misfires, stalling, and engine damage.
Reported in 7 NHTSA complaints
3
Variable Valve Timing (VVT) / Camshaft Phaser Failure
High severity
VVT components or camshaft phasers slip out of synchronization, causing timing over-advanced/retarded conditions (e.g., P0014, P0017) and resulting in misfires and stalling.
Reported in 4 NHTSA complaints
4
Ignition Coil Failure
Medium severity
Faulty ignition coils can cause engine misfires, stalling, and loss of power. Look for a flashing check engine light and specific cylinder misfire codes.
Reported in 2 NHTSA complaints
5
Spark Plug Wear/Failure
Low severity
Worn or fouled spark plugs lead to incomplete combustion and misfires. Often replaced alongside ignition coils during misfire diagnosis.
Reported in 2 NHTSA complaints
6
Engine Control Module (ECM) / Software Issues
Medium severity
Faulty ECM or outdated software can cause persistent misfires and stalling that do not resolve with mechanical repairs like coil or plug replacement.
Reported in 1 NHTSA complaint
7
Vacuum Leak
Medium severity
Unmetered air entering the intake manifold leans out the air/fuel mixture, causing random/multiple misfires. Look for cracked hoses or intake gasket leaks.
Common cause
8
Fuel Injector Failure
Medium severity
Clogged or failing fuel injectors prevent proper fuel delivery, leading to lean misfires. Confirmed by injector flow testing or moving the injector to see if the misfire follows.
Common cause
9
Low Fuel Pressure
Medium severity
A failing fuel pump or clogged fuel filter reduces fuel pressure, causing a lean condition and random misfires across multiple cylinders.
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