Q: Ignition Coil 5 is bad

Ignition coils can be a very tricky component to diagnose and there is virtually no way to tell when one may or may not fail without pulling one apart and doing extensive testing. Often times when they fail, it can happen over an extended period of time and will generally happen intermittently and randomly. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted repeatedly The insulation develops small fractures that open when heated and close when cooled. When open, they allow shorting of coil windings and decrease or eliminate the coil’s ability to function. This type of temperature cycling happens because every time you shut the engine off, the fan stops running, the coolant stops flowing and the temperature under the hood rises. Every time you start the engine again the coolant flows, the fans turn on, and the temperature drops. When this heat dissipates and is absorbed under the hood, it is trapped causing this cycling effect. It is a matter of personal preference as to whether or not you prefer to replace all of the coils at the same time. It may be beneficial to do so since it may be a bit more efficient from a labor standpoint, however replacing them all does not necessarily guarantee that one of them may not fail in the future. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle to properly diagnose your ignition system.