According to the code check, I have a misfire on cylinder 8. The car seems to run fine, except occasionally when I'm sitting at idle. When I'm idling, it sometimes stumbles or shudders, but it rarely dies. I had the spark plugs changed before. Could a bad spark plug cause this, or might there be something else going on?
It could be the spark plug, ignition coil, or coil boot causing the misfire. You may also have dirty fuel injectors that need to be cleaned. Have the ECM scanned to see if the misfire code is P0308. This code refers to cylinder #8. If so, check the spark plug, coil, and boot for issues and replace them if you find any. Otherwise swap the #8 and #7 coil and boot. If the misfire happens again and moves to cylinder #7, then you know to replace that coil and boot to fix the issue. If you need assistance, a certified mobile mechanic from YourMechanic can inspect the cause of the misfire at your home or office.