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P0300 – Random/Multiple Cylinder Misfire – Hyundai/Kia GDI (Hyundai / Kia 1.6 GDI / T-GDI)

Fault code P0300 means "Random/Multiple Cylinder Misfire – Hyundai/Kia GDI". It is common on 1.6 GDI / T-GDI (i30, Tucson, Ceed, Sportage, Kona, Niro), 2.0 / 2.4 GDI (ix35, Tucson, Sportage, Sorento), 1.0 T-GDI (i20, i30, Ceed, Stonic) engines. Below are the real-world causes, step-by-step tests and OEM part numbers.

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P0300 quick summary

Fault codeP0300
MeaningRandom/Multiple Cylinder Misfire – Hyundai/Kia GDI
SystemPowertrain (Engine & Transmission)
VehiclesHyundai / Kia
Common on1.6 GDI / T-GDI (i30, Tucson, Ceed, Sportage, Kona, Niro), 2.0 / 2.4 GDI (ix35, Tucson, Sportage, Sorento), 1.0 T-GDI (i20, i30, Ceed, Stonic)
SeverityHigh
Can I drive?Only gently and briefly. If the check engine light flashes, stop – a misfire can damage the catalytic converter.
Repair cost€30 – €900

Symptoms of P0300

  • Shaking or rough idle, especially cold
  • Flashing check engine light
  • Loss of power and hesitation
  • Higher fuel consumption
  • Cylinder codes P0301–P0304

Most common causes of P0300 (most likely first)

Mechanic's Pro Tip

Direct-injection Hyundai/Kia engines build up carbon on the intake valves, which causes misfires on cold start. Start with coils and plugs (swap the coil to see if the misfire follows it), then check injectors. If the misfire is worst cold and fades when warm, an intake valve cleaning (walnut blasting) is often the real fix.

  1. 1.Faulty ignition coil

    Most likely

  2. 2.Worn spark plugs

  3. 3.Carbon build-up on the intake valves (direct injection)

  4. 4.Leaking or faulty injector

  5. 5.Low compression

Step-by-step diagnostic guide

  1. 1

    Read all codes and misfire counters to find the cylinders.

  2. 2

    Check spark plugs and swap coils between cylinders.

  3. 3

    Test injectors and fuel pressure.

  4. 4

    Inspect intake valves with a borescope for carbon build-up.

  5. 5

    Do a compression test if the misfire stays on one cylinder.

How do I read fault codes? →Where the OBD2 port is, which scanner to use and how to read and clear codes step by step.

Frequently asked questions

Why do GDI engines get carbon build-up?

Fuel is injected directly into the cylinder, so it no longer washes the intake valves. Oil vapour from the crankcase ventilation bakes onto them.

Is a misfire related to P1326?

Not directly, but a knocking engine with low oil should be checked for P1326 and bearing wear.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.