Can Spark Plugs Go Bad If You Let Your Car Sit


The spark plug is a part of your vehicle that delivers the electric current to the combustion chamber inside the engine, igniting the fuel/air mixture and allowing the engine to start running. The electric spark ignites the mixture while keeping the pressure within the engine. 

If it malfunctions, it can cause many problems. However, they don’t go bad that often, and many manufacturers claim they won’t ever go bat from sitting. So, can a spark plug go bad from sitting?

Under normal conditions, a spark plug can sit in a vehicle for years without going bad, even if you didn’t ignite it once during that period. If stored properly brand-new, it can virtually sit forever. Other conditions such as oil or carbon pollution can make it go bad, though.

If you are unsure if your spark plug is causing you problems and should you replace it, you’re in the right place. If the vehicle was sitting in place for a long time, it’s probably some other problem in question and not the spark plug, but it’s always good to know how to deal with the plugs if they need replacement or cleaning.

Can a spark plug go bad from sitting?

Provided there are no special conditions, spark plugs can sit inside a vehicle for years without going bad. Other parts of the fuel and ignition system tend to be more prone to going bad with time, but spark plugs have a long-lasting life. 

They are well secluded inside the combustion chamber, so external influences don’t affect them. Also, a regular spark plug is made of parts that aren’t sensitive to rot or decomposition with time. Other things can cause spark plugs to go bad, but it’s not sitting still.

If we’re talking about brand-new spark plugs still in the packaging, there’s an even smaller chance of them going bad because of sitting, especially if they are stored properly.

How long does a spark plug last?

As I’ve mentioned earlier, spark plugs tend to have a very long lifetime. They can sit for extended periods without breaking or going bad, unlike some other car parts. Spark plugs found in a car that hasn’t been moved in a while can last for years in such a condition, although problems like clogs in the injection system can occur.

There’s a lot higher chance that your spark plug will go bad if you’re driving your car regularly than from your car sitting for a long time. When we talk about new, packaged plugs, they can last a lifetime without going bad.

The only thing you need to keep in mind is keeping them stored properly. Try keeping them away from damp, humid places. Also, don’t throw them around, and don’t expose the package to direct sunlight, as the heat can reduce the plug’s effectiveness.

What causes spark plug malfunctions?

There are many possible reasons why your spark plugs can go bad. They all have a lifetime, and they usually go bad right where you’d think they will, depending on how many years and how many miles you’ve used them for. However, many things can cause them to break much faster than anticipated.

Of course, time is their biggest enemy. As we already learned that new spark plugs stored in their package virtually never go bad, so I’ll concentrate on spark plugs that are in use.

To have your spark plugs working properly, they need to be clean. That’s why bad fuel filters are the most common reason that spark plugs go bad early. If your fuel filters don’t work properly, it will cause the accumulation of dirt, oil, and residue on your spark plugs, causing damage and a shorter lifespan for your plugs.

Next, you need to make sure that your spark plugs are suitable for your vehicle. There’s a small gap between the metals on the tip of the plug, which has to be suitable for your engine. If it’s not suitable, it will silently wear the plug out, causing it to go bad.

If your engine tends to overheat because of cooling malfunctions, it will most likely damage the spark plugs. However, if you have problems with the cooling, bad spark plugs will be the least of your problems if you don’t fix the malfunction quickly.

A flooded engine will most likely cause a spark plug malfunction. Wet spark plugs can happen either by a slow, steady oil leak inside the chamber causing residue on the plug or by too much fuel intake without ignition (usually happens when you’re trying to start a cold engine).

Finally, you should be careful about carbon residue on your spark plugs. As I said, they have to be clean, and if there’s carbon buildup on them, they’ll go bad fast. Carbon buildup inside the chamber happens when there’s too much start-and-stop action or when the vehicle stands still without driving for too long.

How to know if your spark plug went bad?

You might notice some changes in your vehicle’s performance. Many different issues can cause those changes, so it’s important to know what to look for to find out which part of the system is malfunctioning. 

There are many symptoms your car can display when a spark plug goes bad. Of course, several different problems can cause the same symptom, so you should always check everything out when seeing unusual behavior in your vehicle.

If your vehicle starts burning more fuel than usual, it’s probable a bad spark plug that’s causing it. Slow to no ignition makes the engine pull more fuel in. Note that bad spark plugs aren’t the only reason for poor fuel economy, so you should always double-check everything.

The most common symptom of a bad spark plug is your vehicle starting very hard or not starting at all. Spark plugs are responsible for ignition, so if you have trouble starting your vehicle in normal conditions, it’s most likely a bad spark plug that’s causing it.

Also, if you manage to start your car but feel like it lost its acceleration power or feel an unusual vibration when accelerating, a bad spark plug might be the problem. In this case, you’ll always remain at a low RPM, even if you put the “pedal to the metal.”

Other symptoms might be rough vibrations when idling, engine misfiring, etc.

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