P0303 Toyota 4Runner
Cylinder 3 Misfire Detected · Powertrain Code · High · Repair: Moderate
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 Toyota 4Runner 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 Toyota 4Runner.
This repair is rated moderate, meaning some experience and specialty tools required.
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 Toyota 4Runner.
Common Causes on Toyota 4Runner
- Cylinder 3 misfire — worn Denso iridium spark plug past 120k mile interval
- Failed ignition coil on cylinder 3
- Clogged fuel injector on cylinder 3
- Intake manifold gasket leak near cylinder 3 port
- Carbon buildup on intake valve (direct injection 2.0T engines)
Symptoms
- Flashing Check Engine Light during active misfire
- Rough running and vibration at idle
- Power loss under load
- Raw fuel smell from tailpipe
Notes for Toyota 4Runner
If multiple misfire codes appear together (P0300 + P0303), suspect a shared cause like low fuel pressure or vacuum leak rather than a single cylinder issue.