If your car's spark plugs are bad, you'll likely see one or more of the following symptoms:
1. The engine is hard to start.
2. The engine misfires.
3. The engine runs rough.
4. The engine is less powerful than usual.
5. You're getting poor fuel economy.
These symptoms can be caused by other problems, so it's important to have a mechanic check things out if you're not sure what's going on. If they confirm that your spark plugs are the issue, then the good news is that they're an easy and relatively inexpensive fix!