When Should I Change Spark Plugs?
Unless you are a car junkie or certified auto mechanic you probably know very little about what makes your car tick. Most people know that the engine is what makes the car go but don’t really understand how it works. Whether your daily driver is a Ferrari or a Ford, new or old, your engine spark plugs make it go. That’s why it’s important to understand what spark plugs are and when they should be changed. Here are a few tips to help you recognize problems with your spark plugs.
What are spark plugs?
To give you some idea of what a spark plug is, just visualize a tiny but powerful lightning bolt. With each bolt of lightning, an explosion of fuel and air is set off in your engines cylinder chamber. Depending on your car, you may have anywhere from 4 to 8 spark plugs. Some larger vehicles can have as many as 12 spark plugs. But whatever number you have, each one is generating its own little explosion inside the engine. That is where the magic happens, so it is important to pay close attention to any signs of trouble.
How do I know when to change spark plug?
With the technology in vehicles today, the chance of a spark plug going bad is remote, but it can happen. After all, the spark plug is made of metal and ceramic so any weakness will eventually show itself. Exposure to harsh conditions, high pressure and high heat will eventually take its toll no matter how well made it is. So, if a spark plug does fail, how would you know? Usually it is not hard to identify the symptoms if you are just a little bit observant. Let’s look at some of the warning signs:
- Engine light comes on: the engine light can illuminate for any number of reasons. If it does come on, then it will require a technician or an obd scan tool to diagnose exactly what the issue is.
- Poor acceleration: if your car does not accelerate like it used to then it could be the spark plugs or ignition system. Spark plugs require electric pulses from the computer to fire correctly. Any ignition system issue could disrupt this flow and cause poor acceleration.
- Decrease in fuel economy: even if the ignition system is working perfectly the spark plug is where the rubber meets the road. If it is showing its age or starting to breakdown then you will notice a decrease in fuel economy.
- Engine is misfiring: this is a big one because you can feel as well as hear what is happening. Sometimes this is caused by a bad wire connected to the spark plug. Other times it’s a bad spark plug causing misfiring and poor fuel economy.
- Surging or hesitation when you step on the gas: this indicates that the engine is not responding to your commands. If the engine is sucking in a lot of air, you’ll notice that the engine will speed up (surge) then slow down (hesitate). This is not normal and may indicate a bad spark plug or two.
- Idling roughly: this is like misfiring but not quite as loud. Usually you will notice a mild to severe vibration in the engine. This means that one or more of the cylinders is not firing quite right because of a bad spark plug.
- Hard starting: if your car suddenly cranks more then it used to then this is a sign that your spark plugs are worn. As we have said, all the components in the ignition system need to work together but the spark plug is where the magic happens.
- Check the owner’s manual: car makers do publish a recommended maintenance schedule which can be found in your owner’s manual. If you do this then you will most probably avoid many of the problems highlighted above. It is a low-cost way to ensure that you do not have issues that impact your driving pleasure.
How to change a spark plug
The process of how to change spark plugs is very easy if you have the right tools. The rule of thumb is to replace spark plugs at around 30,000 miles. If you are not sure, refer to your owner’s manual for guidance. Here is a quick overview of how to tackle this job:
- Replace spark plugs one at a time to ensure that you do not accidentally mix up the wires connected to the distributor.
- Do not pull on the wire; only pull gently on the connector to remove it.
- Check the gap on the spark plug to be sure it is within factory specs.
- To replace a spark plug in a hard to reach part of the engine, just insert it into one end of a rubber hose. Then maneuver it into the cylinder hole opening.
- When installing a new plug do not over tighten it.
- When installing the new spark plug it should turn easily, if you encounter any resistance reverse direction to remove the spark plug and fix the problem.
Common problems with spark plugs
As we have said, a spark plug is made of metal and ceramic so any weakness will eventually show itself. Let’s look at the common problems with spark plugs:
- Deposits build up on the electrode: this is usually caused by an improper mixture of gas and air. Buildup on the electrode will usually cause pre-ignition of the fuel which is like a pinging sound.
- The dreaded expanding electrode gap: when the gap increases it becomes more difficult to create a spark (lightning bolt). The right gap ensures that there is a consistent spark created to ignite the air-fuel mixture.
- Old age: spark plugs are under a lot of pressure to perform and as they age their strength and efficiency will decrease. In a lot of cases the material that makes up the spark plug will help it endure for a long time. Eventually though, it will eventually start to show its age by failing under pressure.
- Oil finding its way into the combustion chamber: this will really gunk up the works. If oil begins to seep around piston rings or comes in via other openings, the result will be a serious problem. Not to mention a lot of smoke coming out of the tail pipe.
- The tip of the spark plug is overheating: this will cause it to wear out prematurely. This is usually caused by a timing issue which causes an excessive amount of heat to build up in the combustion chamber. If your cooling system is working as it should be, but the engine still runs hot then there is a problem.
Your spark plugs are the most hard-working components in your car. Without them the engine would not run, and you would not be going anywhere. It is hard to visualize the extremely difficult working conditions that the spark plugs need to operate in. From below zero cold to scorching heat, enormous pressure to fuel starvation and oil baths, the lowly spark plug perseveres. This might be a good time to reflect on all that your spark plugs have gone through over the years. Will they make it another season? Maybe it’s time to consider replacing them before you experience one of the warning signs listed above. If your car is in good shape with no mechanical issues, installing a fresh set of spark plugs will keep your engine running strong for years to come.
This is a collaborative article.
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