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Q: The Check Engine Light came on, I hooked it up to my scanner and got the code P0308 (cylinder #8 misfire).

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Engine seems to run fine and I don't notice anything wrong with it when Im driving... do I need to replace my ignition coil or not? What else could be the issue? I don't want to waste money having someone replace my ignition coil if that won't fix my issue. I know my CV boot is cracked so could that be causing the problem?

My car has 121000 miles.
My car has an automatic transmission.

A: An easy way to isolate if the ignition coil...

An easy way to isolate if the ignition coil is the problem is to swap the #8 coil with another cylinder. Swap the #8 coil with the coil from the adjacent cylinder, then clear the codes. If the code remains for cylinder #8, then there are other issues such as the spark plug, wiring, or a signal issue from the PCM. Also, an injector with a poor spray pattern can cause the misfire as well as a mechanical issue with cylinder #8 such as a valve or compression issue.

If the fault code moves with the ignition coil, then odds are you do have a bad ignition coil. If the coil is at fault, you may want to consider replacing them all at the same time. More commonly than not, when one coil fails, one or more will soon fail as well. Changing them all at the same time alleviates having to go through this 7 more times over the next several months. Otherwise replacing them as they fail is not a problem.

To avoid any unnecessary repairs, have a certified technician, such as one from YourMechanic, diagnose the Check Engine Light firsthand and help you resolve the issue.

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