How to resolve P0303 cylinder 3 misfire detected?

[VeraLynn]

P0303 cylinder 3 misfire detected should first check spark plugs, ignition wires, and ignition coils, and replace spark plugs or ignition coils in a timely manner. Below are relevant details: 1. Data stream: For diagnosing engine misfires, sometimes just reading the engine data stream isn't sufficient, and an oscilloscope may be needed for further judgment. 2. Factors: Factors to consider for ignition include ignition timing, whether the spark plugs are functioning properly, whether the resistance of the high-voltage wires is within the standard range, and whether the ignition coils are working correctly (whether power and signal wires are securely connected). Also, check if the engine control unit is functioning properly (including signals provided by CAN data). It is recommended to use diagnostic tools for inspection whenever possible.

[MacPresley]

Don't panic when you see the P0303 trouble code, focus on inspecting the ignition system of cylinder 3. I've dealt with similar issues myself - first try the simplest solution: swap the ignition coils between cylinder 3 and its adjacent cylinder, clear the code and drive for a while. If the fault moves to the new cylinder, it means the ignition coil is faulty. Spark plugs are another common culprit - remove them to check if the electrode gap is too wide or if there's carbon buildup. Clogged fuel injectors can also cause misfires; try adding a fuel system cleaner that matches your fuel grade to the gas tank. If none of these work, you'll need to check cylinder compression and cylinder head sealing. My neighbor's car once had misfires due to slight leakage from the cylinder head gasket, which requires professional equipment to diagnose. Remember to address basic issues before considering major repairs.

[VanNova]

When dealing with a three-cylinder misfire, systematic troubleshooting is essential. Based on my decade of auto repair experience, this sequence saves the most time: First, unplug the ignition coil connector and listen for changes in engine sound—no reaction indicates a coil or wiring issue. Next, use a borescope to inspect the spark plug condition; replace if the ceramic body is cracked or the gap exceeds 1.1mm. Then, use a diagnostic tool to read the fuel trim values—STFT exceeding ±10% may point to a faulty fuel injector. Finally, perform a compression test; if below 8bar, consider valve sealing or piston ring problems. Don’t forget to check the intake pipe behind the air filter—last week, I encountered a case where a rodent-chewed hose caused a lean mixture in the third cylinder. These tests are best performed at a repair shop, as DIY attempts can lead to misdiagnosis.

[Leon]

P0303 priority checks three things: ignition coil, spark plug, and fuel injector. If you're doing it yourself, buying a spark plug socket for inspection is the most practical approach. NGK or Bosch spark plugs are recommended to be replaced every 40,000 kilometers. Pull out the coil and smell for any burnt odor - if present, it must be replaced. For clogged fuel injectors, try revving the engine to 4000 RPM and maintaining it for a few minutes; sometimes this can clear carbon deposits. If the check engine light is flashing, do not continue driving - misfires can damage the catalytic converter, and replacing one costs around five to six thousand. Last time my car had this issue, it turned out to be a loose ignition coil connector; simply re-securing it fixed the problem.