P0303 Hyundai Elantra
Cylinder 3 Misfire Detected · Powertrain Code · High · Repair: Easy
What is P0303?
Misfire detected in cylinder 3. Typically caused by a worn spark plug, bad ignition coil, faulty fuel injector, or low compression in that cylinder.
When the Hyundai Elantra triggers code P0303 (cylinder 3 misfire detected), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the Hyundai Elantra.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Hyundai Elantra.
Common Causes on Hyundai Elantra
- Worn spark plug on cylinder 3 beyond service interval
- Failed ignition coil pack on cylinder 3
- Fuel injector clogged or sticking on cylinder 3
- Intake valve carbon buildup on cylinder 3 (GDI)
- Low compression from engine bearing issue on Theta II
Symptoms
- Check Engine Light flashing during misfire
- Rough idle
- Noticeable power loss
- Vibration at idle
- Poor acceleration
Notes for Hyundai Elantra
Swap the coil from cylinder 3 to another cylinder to see if the misfire follows; this confirms a coil issue cheaply.