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Nissan Altima 2002 P0300/P0303 Misfire: Repeated Coil Failures and Root Cause Analysis

Model: Nissan Altima Fault Code: P0302 Posted: 2015-08-14 08:05

I've been experiencing recurring misfire issues on my 2002 Nissan Altima, with the check engine light coming on and fault codes such as P0301 and P0303 appearing over time. Last year, the system flagged a misfire in cylinder 1 (P0301), which I resolved by replacing the ignition coil for that cylinder — after which the issue disappeared temporarily. A few weeks ago, the check engine light returned with a misfire detected in cylinder 4. I replaced the ignition coil on cylinder 4 again, and the problem went away for several days before returning. Recently, after changing the same coil once more, I observed four days without any check engine light activity — then the system triggered P0300 (general misfire) followed by P0303 and a separate code P0455 indicating a catalytic converter issue. My question: What could be causing this 'travelling' misfire? While ignition coils appear to be failing repeatedly, I suspect there may be an underlying cause — such as a faulty oxygen sensor. Even without specific O2 sensor codes, I believe it might affect air-fuel mixture balance and contribute to misfires. Could fuel delivery or combustion issues be at play? The spark plugs are OEM and have been in use for two years; visually they appear fine, and the ignition wires are also intact. I've tried using ignition system cleaners with no improvement. I'm seeking expert insight into possible root causes beyond just coil failure — especially whether fuel quality or sensor performance could be contributing to this recurring pattern.

Related fault codes
P0302
Comments (3)
Anonymous 2015-08-14 11:58

You're currently using Nissan OEM parts, including spark plugs. Consider other components in the ignition system such as a faulty condenser or capacitor — these can degrade over time and contribute to misfires. Also, fuel delivery issues should not be overlooked; misfires are not solely caused by spark or coil failure.

Anonymous 2015-08-14 12:25

Thanks for the reply. The spark plugs are two years old and show no visible wear — both plugs and ignition wires appear in good condition. I've already tried using an ignition system cleaner, but it hasn't resolved the issue. While coil replacement temporarily fixes the problem, it often returns on a different cylinder, suggesting a deeper systemic cause.

Anonymous 2015-08-14 12:36

A systematic approach is needed — note that your original post didn’t specify the engine year or model variant. If spark plugs are OEM, poor performance could still result from degraded electrodes or contamination. Always use genuine OEM coils — aftermarket units often have inconsistent quality and can lead to recurring failures. A condenser or capacitor in the coil wiring harness may also be failing silently. For a more accurate diagnosis, using an OBD2 scanner to monitor real-time misfire events, fuel trim values, and oxygen sensor voltages would provide critical data.