In any event, it's a symptom of fuel fouling your spark plug. This could also indicate problems with ignition or the heat range. If the tip and side of your spark plug is shiny that might be an indication that you have a rich fuel mixture. It s possible to clean this coating off and get the plug working again.
The carbon coating makes it extremely difficult for your spark plug to actually spark properly. This comes from running with too much fuel, bad wiring, leaking injectors, and other potential problems with the combustion reaction.
If the top of your plug and the sides are black like they've been on the barbecue, that's a sign you've got carbon build-up. That causes a hesitation and jerking and lurching motions when you try to start the car. If the spark doesn't work right away, the second cylinder in your engine may have to take over and get things started. This is due to the combustion reaction not occurring exactly right when you turn the key in the ignition. When you first start your vehicle, if you're finding that the engine seems to struggle to get going, like it takes a moment before it actually engages, that can be a problem with your spark plugs. Even worse than that, you'll end up getting a worse performance as a result so you're paying more to get less. That's going to require your engine to push a little harder and use more gas to try to compensate for what's missing, which in turn means you're going to be heading to the gas station more often. When spark plugs aren't working then the gas that your injectors are spraying into your engine is essentially just being wasted. If it happens on a routine basis you can almost guarantee that it's a spark plug causing it and will also lead to some severe damage over time. If your spark plugs can't produce a spark, that cylinder of your engine will not be able to have a combustion reaction, and that is essentially just what a misfire is. That's almost a textbook definition of a poor spark plug in fact.
One of the most common problems with a bad spark plug is that your engine is going to misfire. Aside from the visuals, there are also a number of performance issues that can help you identify problems with your spark plugs as well. You should get a good idea of what a spark plug looks like when it's brand new so that if yours are having problems you can easily identify it just from a quick visual inspection. If you are experiencing problems with your spark plugs there are signs you can be on the lookout for to let you know something needs to be done about it. When you're checking your spark plugs you need to do each one in turn to see how many, if any, are not working correctly. Regardless, if you have a 4-cylinder vehicle, you have four spark plugs that could have problems. There are actually some cars that will have more than one spark plug for a cylinder but that's not the normal design for engines. Remember that your car has as many spark plugs as it has cylinders. Check out a number of the signs and symptoms that will indicate your spark plugs are having problems and need to be replaced. Regardless of the projected lifespan of your spark plugs, there are a lot of factors that can also greatly reduce the life of your plugs. If you're not sure what kind of plugs you have, it's a good idea to check and see so you have an idea how long you can expect them to last before they start giving you problems. On the higher end of things, those platinum and iridium plugs are the ones that are going to last upwards of 100,000 miles. Obviously, that's a really big range to deal with, but those factors we mentioned earlier really play into how it works out for you. In general, you're probably going to have to replace your spark plugs anywhere between 30,000 miles and 100,000 miles. Spark plugs made with metals like platinum, iridium, and so on are designed to handle high heat and last much longer than cheaper copper and nickel ones. Cheaper spark plugs are obviously not going to last as long as higher quality ones. This includes the kind of spark plugs that you bought, the make and model of your vehicle, and how you drive the car as well. A number of factors can affect the life span of any given spark plug. There's no hard-and-fast rule for exactly how long a spark plug is going to last.