Spark plugs will need changing periodically during your car’s life. Luckily, the symptoms of a damaged spark plug are fairly obvious, including poor fuel economy, slow acceleration, and engine misfires. Replacing them is a fairly simple process, too, though many people still turn to a mechanic to get the job done. However, spark plugs are also excellent indicators of your engine’s overall health. Specifically, the electrodes at the ends of spark plugs can be used as a diagnostic tool to help you discover critical problems that could soon leave you with massive repair bills.
The nice thing about using spark plugs to understand your engine is that these symptoms are universal, no matter what kind of vehicle you use. Cars, trucks, ATVs, lawnmowers, and even boats will all produce similar effects on the electrodes, and they can be easier to check than your engine.
Brown or Gray Deposits
Normal spark plugs may have grey or brown deposits on their electrodes, especially on the side. This is a normal spark plug that doesn’t need changing and isn’t a warning sign regarding other problems in your engine. However, if you’re experiencing problems with your vehicle, then you need to take it to a mechanic to diagnose the problem regardless of your normal-looking spark plugs. Remember to flush out any dirt with compressed air before you reinstall the spark plug.
Worn-Down Electrodes
These are spark plugs that need to be replaced. The wearing down of spark plugs is natural as you rack up the miles, and you’ll probably have noticed several symptoms showing that your spark plugs are deteriorating. If your engine is misfiring or the car isn’t speeding up as it should, your spark plugs have probably just run the course of their life.
If you intend to replace them yourself, make sure you know the proper size to get first. This information should be in your owner’s manual, although a mechanic could tell you as well.
Broken Electrodes
Broken electrodes don’t point to anything catastrophically wrong, either. They just mean it’s likely that the wrong kind of spark plug was installed. That doesn’t mean that the wrong size of spark plug can’t damage your engine, as spark plugs that are too long can cause damage, but it does mean that the problem lies solely with the spark plugs and not with another problem that trickled down to them. If your mechanic put in the wrong spark plugs, you should be entitled to a free repair. Your manual should also have the right size listed in it.
Oily Spark Plugs
If you do maintenance on two-stroke engines, such as chainsaws, you may have noticed oil on the spark plugs, usually on the electrodes. In a two-stroke engine, this is a normal occurrence. However, if you see oily electrodes on the spark plugs of a four-stroke engine (vehicles), this is a cause for concern.
Oil on your car’s spark plugs indicates a few different things, such as too much oil being mixed with the gas or that the oil is too thin in viscosity, allowing it to slip past the piston. Unfortunately, it can also point to some severe engine problems. If the pistons or valve guides are worn out or experiencing some other problem, oil can leak into the cylinders. If it’s the piston rings, the engine won’t start easily. Regardless of other symptoms, you’ll need a mechanic to take care of the problem.
Sooty Electrodes
If you notice soot on your spark plugs, specifically around the insulator tips and electrodes, you may have a carbon-fouled plug. There are a few things that can cause this problem.
Some reasons there may be dry, soft carbon deposits on your spark plugs are how you’ve been driven. Idling your vehicle for a long time, neglecting to change your air filter, and frequently driving at low speeds are some reasons your plugs may be carbon-fouled.
It could also be that your air-fuel mixture is too rich. If you also have low gas mileage, this could be the reason. It means you have too much carbon growth on your engine, which is contributing to the rich mixture.
If your spark plug’s gap is too wide, it can also cause this problem. The spark plug won’t burn correctly and will become sooty. To remedy this, you’ll either need to have a mechanic set the gap, do it yourself with a gap tool, or replace the spark plug. Many spark plugs come with preset gaps nowadays, as long as you know what kind to get.
Wet Spark Plugs
If your spark plugs are wet, it could be because either the engine is flooding or an ignition cable is bad. The engine can flood when you try starting the engine multiple times without success. You can either wipe them dry yourself or just wait for them to dry naturally.
Burns and Heat Damage
Burns on the insulator tip, electrodes that look partially or wholly melted, or white deposits are all signs of a burned spark plug. An overheating engine, a loose spark plug, an incorrect heat range, an incorrect air/fuel mixture, or even incorrect ignition timing can cause these. The spark plug should be replaced and a trip to the mechanic is in order to further diagnose the problem.
What if There’s a Problem with Your Spark Plugs?
Most of these signs show that your car’s spark plugs need to be replaced. Some people feel comfortable doing this themselves, while others will want help. Remember to ensure you’ve got the correct size of spark plug before you install it. If you’re unsure, check your owner’s manual or ask your mechanic.