What is a Resistor Spark Plug (A Definitive Guide)

A resistor spark plug is a type of spark plug that has a resistor in the tip. The purpose of the resistor is to suppress radio frequency interference (RFI). It does this by creating a small electrical resistance in the path of the high-frequency current.

This slows down the flow of current and limits the amount of energy that can be conducted through the air. The result is less RFI noise.

Sparkplug resistor vs non resistor hot resistance test

If you’re a car enthusiast, then you’ve probably heard of resistor spark plugs. But what are they and why are they so important? Resistor spark plugs are designed to suppress electrical interference that can cause misfires in the engine.

They do this by creating a small resistance between the plug’s electrode and the spark plug boot. This resistance helps to prevent interference from things like ignition coils, radios, and other electronic devices. Resistor spark plugs are especially important if your car has an aftermarket stereo or other electronic accessories.

Without a resistor spark plug, these devices can cause all sorts of problems for your engine including missing or weak sparks. In some cases, it can even damage the ignition coil! So if you’ve got aftermarket stereo or other electronics in your car, make sure to upgrade to resistor spark plugs.

It’s a small investment that could save you a lot of headaches (and money) down the road.

When to Use Non-Resistor Spark Plugs?

When to Use Non-Resistor Spark Plugs?

If your vehicle is running a bit rough, it might be time to switch to non-resistor spark plugs. Here’s what you need to know about when to use them. Non resistor spark plugs are designed for vehicles that run-on higher-octane fuel.

If your vehicle is having trouble igniting the fuel properly, switching to a non-resistor spark plug can help. They also work well in dirty or fouled up engines. If your engine is full of carbon deposits, a non-resistor spark plug can help break through that build-up and get things running smoothly again.

Keep in mind that non-resistor spark plugs will create more sparks than regular plugs, so they’re not ideal for use in street legal vehicles. They’re perfect for race cars and other high-performance vehicles though!

Which is Better a Resistor Or Non-Resistor Spark Plug?

Which is Better a Resistor Or Non-Resistor Spark Plug?

There is no definitive answer to this question as it depends on a number of factors, including the make and model of your vehicle, driving conditions, and personal preferences. In general, however, resistor spark plugs are better suited for street driving while non-resistor plugs are better for off-road or high performance applications. Resistor plugs help to suppress electrical interference from radios and other electronic devices, which can improve ignition timing and prevent misfires.

Non-resistor plugs tend to provide a hotter spark that is more resistant to fouling in dirty or dusty conditions. Ultimately, the best type of spark plug for your car will depend on your specific needs and driving habits.

What is the Difference between a Spark Plug With a Resistor?

If you’re shopping for spark plugs, you may notice that some of them have a resistor while others don’t. So what’s the difference? A spark plug with a resistor is designed to reduce electrical interference.

That means it will help your car’s radio reception and other electronic systems function more smoothly. It also helps prevent cross-talk between wires, which can cause engine misfires. Spark plugs without resistors are less expensive, but they may cause some interference problems.

If you’re not having any issues with your car’s electronics, though, they’ll work just fine.

What is a Non-Resistant Spark Plug?

What is a Non Resistant Spark Plug?

A nonresistant spark plug is a type of spark plug that does not have a resistor in it. This means that the spark plug can produce a higher voltage than a regular spark plug, which can help to improve the performance of your engine.

How Do You Check a Resistor on a Spark Plug?

In order to check a resistor on a spark plug, you will need a multimeter. First, remove the spark plug from the engine. Then, use the multimeter to measure the resistance between the two terminals on the spark plug. If the resistance is within the specified range, then the resistor is working properly.

How Do You Check a Resistor on a Spark Plug?

Frequently Asked Questions (FAQs)

How does a resistor spark plug contribute to engine performance?

By reducing electromagnetic interference, a resistor spark plug ensures a stable and consistent spark. This contributes to smoother combustion, improved fuel efficiency, and better overall engine performance.

Can resistor spark plugs be used in any vehicle?

Yes, resistor spark plugs are versatile and can be used in most vehicles, including cars, trucks, and motorcycles. They are especially beneficial in vehicles with electronic ignition systems.

Are resistor spark plugs necessary for modern engines?

While not mandatory, resistor spark plugs are recommended for modern engines with electronic systems. They help maintain the integrity of these systems and prevent potential interference issues.

How can I identify a resistor spark plug?

Resistor spark plugs typically have an “R” in their part number, indicating the presence of a resistor. Additionally, the ceramic insulator may have a distinct color or markings denoting its resistance.


A resistor spark plug serves a crucial role in the efficient functioning of internal combustion engines by minimizing electromagnetic interference and radio frequency interference. This innovative component, equipped with a built-in resistor, successfully suppresses potential disruptions in the electronic systems of modern vehicles. By reducing the electrical noise generated during the ignition process, resistor spark plugs contribute to smoother engine operation, improved fuel efficiency, and enhanced overall performance. As automotive technology continues to advance, the resistor spark plug stands as a testament to the ongoing efforts to optimize combustion processes and ensure the reliability of our vehicles in the face of evolving challenges.