Car spark plugs are small items but they play an important role in the ignition. If one goes bad, it can cause a serious engine malfunction. So, why do spark plugs go bad? If you know these factors, you may prolong their life.
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How Do Spark Plugs Work?
Every spark plug has a positive electrode, an insulator cap covering it, and a negative electrode. The electrodes are made of different metals or alloys. The positive electrode is made of platinum or iridium, whereas the negative electrode is made of tungsten. These two electrodes are pressed into the preformed hexagonal leaded cylinder by hand without machine tools. A spark is formed when an electric current passes through the electrodes to create an explosion in the cylinder.
What Happens When a Spark Plug Goes Bad?
All engine values and components matter when it comes to overall engine performance. But spark plugs are not as important as most people think they are. A bad spark plug can cause your engine to crank slowly or start with difficulty, but the vehicle will keep running if you replace it. You can determine if a spark plug is bad by removing it and examining its tip. If the tip has turned black, the plug may be worn out and needs replacing.
How Long Do Spark Plugs Last?
A spark plug can last up to 20,000 miles if you follow the maintenance schedule of your vehicle. If the vehicle keeps misfiring or runs poorly, then one or more spark plugs may need replacing. Sometimes, misfiring can result from bad ignition wires or distributors, too. But simple tests like squeezing the plug with pliers (they should feel hard) and looking at their condition can help you make early replacements.
Why Do Spark Plugs Go Bad?
Car spark plugs go bad for various reasons. Here are the most common ones:
1. Rust corrosion.
Corrosion of the electrode’s metal can lead to an electrical short that prevents spark at the spark plug. This results in loss of performance and may damage other components, too. To prolong their lives, you can apply anti-corrosion oil to the rubber boot around each spark plug each time you do an oil change.
2. The insulator sleeve
The insulator sleeve surrounding the electrodes becomes dirty, cracked or wavy. Dirt can cause electrical shorts that prevent spark to form. To prevent this, clean the insulator by scraping off rust and other deposits with a fine-grade wire brush. Alternatively, you can replace it to avoid loss of performance.
3. Insufficient heat from the engine
Insufficient heat from the engine to ignite the spark plug. The heat from the engine needs to be at least 300° F (150° C) to ignite gas in the combustion chamber – regardless of how long it sits idle between starts. Incorrect heat can result in the accumulation of gas or moisture in the combustion chamber which can limit spark performance (clogging). This problem usually occurs under high load (acceleration, sport driving, heavy loads on one side of the vehicle).
4. Using Leaded Gas
Car manufacturers recommend using unleaded gas to ensure spark plug performance as leaded gasoline creates more bypass products, which is carbon buildup.
5. Bad distributor or ignition system
When the distributor or ignition system is not working correctly, too much spark can be produced which can cause misfires, stuttering (stutter-stepping), and poor acceleration results (the engine loses power on acceleration). To determine this, you need to receive a diagnostic test that reveals these signs. You also need to replace the entire system, if possible.
6. Incorrect Spark Plugs Gap
The gap is the gap between the electrodes. If it is too small, the gap will cause a short and your car will not run. However, if it is too big, the spark can jump across and can cause you to lose power and misfire. The gap needs to be 0.030″ for most vehicles which means that you should measure with a feeler gauge or gap gauge with this gap value.
7. No Maintenance
If your vehicle is not maintained properly, you need to replace spark plugs after only 15,000 to 20,000 miles; but if you maintain your vehicle regularly and check the spark plugs regularly, then your spark plugs can last up to 20,000 miles. However, the use of incorrect oil and not having regular maintenance done on it can shorten its life.
Symptoms Of Bad Spark Plugs
Here are some of the symptoms of bad or defective spark plugs:
1. Slow Cranking
If you experience a slow crank at startup, you may need to replace one or more of your spark plugs. Spark plugs should last up to 100,000 miles without needing replacing if they are new and in good condition. If you don’t drive your car daily and only drive it every few months then the ignition and the starter may be partially seized. This is because of the non-use of the car for extended periods. This can also cause your engine to spark slowly.
Another reason why it may be slow is because of the engine’s ignition coil pack. The coil pack contains a number of ignition coils that are used to produce the high voltage electricity needed to ignite the fuel in each cylinder. When the coils fail, it will retard the spark timing and cause slow cranking.
2. Car Stalling
A misfire at certain points in your engine’s RPM range will result in installing problems. For example, when you drive at a certain speed in a location where your car stalls, the misfire is in that particular range in RPM. If your spark plugs go bad and one or more sparks slightly miss, this slight miss will result in the car stalling. If you replace the spark plugs and it continues to happen, you may need to replace spark plugs.
3. Tranny Problems
A misfire can cause transmission problems by causing a damaged distributor, carburetor, fuel injector orifice plate. The damaged orifice plate is caused by carbon deposits. Over time, the carbon deposits collect on the orifice plate and do not allow sufficient fuel to pass through. This causes your transmission to shift roughly and may cause your engine to burn more fuel than usual.
4. Misfiring Engine
A misfire can cause your engine to sputter at the RPM that has the misfire in it. It will also cause your engine’s speed at any RPM to vary abruptly instead of smoothly with even throttle pressure applied.
5. Fuel Smell
If your car exhibits a strong fuel smell, you may need to replace some of the spark plugs. If your car is like others that run on diesel fuel, then the fuel smell may be due to burning oil or an electrical problem.
To conclude, you should always replace your spark plugs to keep them in good working condition. If you pay attention to your car, make sure the spark plugs are the first things to change when they start producing errors. Remember that when you replace them, do not use any other type of plugin in the vehicle since they might be damaged and cause a problem with the air and the fuel mix inside the car’s engine.
Hi there! I’m Naomi O’Colman. I’ve got years of experience working at an auto repair shop here in Texas under my belt. On top of that, ever since I was a kid I’ve been passionate about the auto industry. Since I’ve joined the team at automotivegearz.com I’ve been enthusiastically sharing my passion and insights with my readers. I’m dedicated to delivering high quality content and helping you stay up to date with the latest automotive trends and products out there!