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Q: Misfiring Cylinder after replacing the plugs three months ago. Is it a chance that the whole batch of plugs may have been defective?

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The check engine light was flashing last week while driving. The scanner at O'Reilly said that cylinder #4 was misfiring. My neighbor put a new engine coil and plug on #4. That solved it. Now, light is on again and scanner says misfire cylinder #3. Same issue? Can it do damage to the car to drive it? Typical cost to have a station to replace? Can it be something else besides coil? We just replaced all plugs and coils less than 3 months ago. The coils were bought from Rock Auto. Chance that the whole batch may have been defective? Thanks.

My car has 116000 miles.
My car has an automatic transmission.

Hi there. The best thing to do is switch the coil over from cylinder 3 to cylinder 1 and see if the misfire continues with cylinder 3 or if it changes to cylinder 1. If the misfire stays with cylinder 3, then either the spark plug or spark plug wire has failed. Or there could be an issue with the cylinder not sealing or getting fuel. If the misfire changes to cylinder 1, then the coil pack is not working. If you need assistance with diagnosing your misfire, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

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