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What might cause a misfire?

My dad’s 97 dodge neon is showing a misfire in the number 4 cylinder. He replaced the spark plug but still getting that code and engine not running smooth. What other things could cause this? Engine has about 130,000 miles on it, had been running fine.

bad plug wire, bad distributor, bad ignitor, bad distributor cap that gets wet or is close to a ground path, new spark plug that is bad or improperly gapped, are just a few of the possibilities.

he is trying to find out what it is, what if any damage is happening to the engine while he is driving it in this condition?

Misfires can be expensive if you keep driving it. He should park it until the problem is discovered and fixed.

due to it being the only car, it is the only means of transportation for my sister to get to and from work.

Replace the plug wires, distributor cap and rotor and see if that cures it…

He replaced the spark plug? Just one? Why not all four? What about the wires?

On this car, common causes of a misfire include carbon tracking on the coil pack or spark plug wires, spark plug tube seal leaks (oil will accumulate in the tube, deteriorating the wire boot and cause arcing. Tube seals are included with a valve cover gasket kit), worn or damaged spark plug, and the list goes on. From there, it’s electronic or fuel problems that can cause a misfire, and last, mechanical issues. Ignition issues are the easiest to troubleshoot, so start there. And yes, driving the car in this condition can and will cause damage, some kinds of damage quite severe and expensive, like melting down the catalytic converter.

Finish troubleshooting the ignition since, as noted, it is the easiest stuff to worry about. If that doesn’t help check the compression.

Misfire doesn’t literally mean a lack of spark. It means a lack of combustion. Combustion requires air + fuel, compressed, and then ignited by spark. So outside of spark issues you have compression, fuel, and air.

No he replaced all 4 and it still is saying misfire in number 4.

Make sure you are getting spark? Next check compression. You can find a great video on misfire diagnosis at Click on the learn more tab at the top and then open the autolite challenge video on misfire diagnosis