Check engine light is on
Engine misfires
Rough idle
Hard starting
Poor acceleration
Reduced fuel economy
Engine stalling
Backfiring
Strong fuel smell from exhaust
Visible cracks or damage on the coil pack
Burn marks or corrosion on the coil pack
Engine runs worse when wet or in damp conditions
Diagnostic trouble codes for misfire or ignition issues
Swap test shows the problem follows the coil pack
Spark test shows weak or no spark from the coil pack