Q: Misfire that got worse after coil pack and spark plugs were changed

The engine can be diagnosed, and the fault pinpointed, if you request a Check Engine Light diagnostic. Trouble codes that refer to parts, in this instance a coil, do not necessarily mean that the part has failed. For example, if I were to merely create a bad connection to a brand new coil, I could generate a trouble code identical to that which you would get if there were a perfectly good connection to a bad coil. The point is you can’t buy parts on the basis of codes; any suspect part has to be tested directly. Autozone does not diagnose motor vehicles or test parts; they only sell parts. What you need is a pinpoint diagnostic identifying EXACTLY what is wrong with the vehicle and then you need to replace only the parts, if any, that are actually faulty. If you request the diagnostic, the responding certified mechanic will get this resolved without any further nonsense. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.