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P0300 - Random / Multiple Cylinder Misfire Detected
P0304 - Cylinder 4
If you need more data, I could look into downloading live data directly from my car to the computer.
1. Later today, I will remove, and take pictures of all 6 spark plugs for visual indicators. Maybe this will correlate to the OBD findings above.
2. Suppose, one or multiple spark plugs are corroded, is it necessary to change the wires also? If a resistance test across the wires is within acceptable specifications, can the same wires be reused? Or do corroded spark plugs also coincide with internal non-visible wire damage? (This could save $75 on the NGK wire set).
3. The NGK plug on this vehicle is a double platinum ($12 x 6 = $72). Per NGK website, there is also a single platinum available that is acceptable for the vehicle ($4 x 6 = $24). For a $50 difference, is it worth it to stay with the original double-platinum plugs.
Completed the repair. Here are my findings (hopefully to assist others):
1. The coil pack had been previously replaced; however, the broken plastic nipples on the coil pack did not correspond to the most fouled spark plugs.
2. Cylinder #1 was the worst - the old plug was completely black. The others just looked worn down, but not with black soot all over. This cylinder also had a broken spark plug boot when removed.
3. All spark plug wires were replaced (not with OEM wires, but an equivalent high-quality NGK wire set).
4. Anti-seize lubricant was applied to the plug threads, and a torque wrench was used to tighten the plugs to 20 ft-lbs.
5. All engine codes were cleared upon starting the engine.
6. During the first minute, there were still mis-fires heard; however, after the car was taken for a quick test drive, the operation and power returned to normal.
7. No additional P03XX codes appeared after a re-scan.
8. Problem appears to be solved for now.
Yes. All the plugs and wires were replaced.