Can Bad Spark Plugs Cause High RPM?

Bad Spark Plugs High RPM

Bad spark plugs can cause a lot of damage to your car and hinder your overall engine performance. From idling to vibrations, a failing spark plug presents numerous symptoms that can make your engine run rough. While idling, they can make your car run at fluctuating RPMs, generate loud noises, and affect fuel efficiency.

But can bad spark plugs cause high RPMs? Yes, bad spark plugs can cause high RPMs.

A bad spark plug can increase your engine’s revs, causing you to hit high RPMs to compensate for the system’s power shortage. This usually happens if you have a dirty or worn-out spark plug.

Let’s discuss how bad spark plugs affect your vehicle’s RPMs!

What is wrong when RPMs are high?

Everything is basically wrong with a high RPM!

It is normal to panic when your car starts reading unimaginable figures, with your tachometer sitting close to the edge and reading high revolutions per minute (RPM). When your RPMs are high, you run the risk of engine failure or overheating.

High RPMs indicate that your engine is stressing itself to its limits. If this continues unchecked, your car will demand more fuel to function, you will experience wear and tear on your engine, and it can compromise your safety and that of other road users.

Can bad spark plugs cause high RPMs?

Yes. A bad spark plug can also cause high RPMs in your cars.

Bad spark plugs create an uneven consumption/burn of the fuel in your engine. The uneven fuel consumption will result in fluctuations in RPMs; in some situations, the RPM will go high.

The bad spark plugs usually cause high RPMs because they are not firing correctly. To compensate for the misfiring, your engine will have to rev up, delivering high RPMs, to match the lack of power. The issue can escalate to overheating or damage to your engine.

Does spark plug affect RPM?

Spark plug affects RPMs by causing a drop or surge in your RPM. The fluctuations in RPM are usually caused by a bad, dirty, or failing spark plug. Your spark plug handles the production of RPM in your car.

When you have a bad spark plug, the plug can’t generate strong sparks. This will prevent the ability of your engine from running smoothly. In this situation, your RPM is affected as your engine and car try to compensate for the engine's loss of power.

What can cause high RPMs?

There are a lot of factors that can cause high RPMs. This should help you understand that bad spark plugs are not the common cause of high RPMs.

Here are some common causes of high RPMs:

  • Transmission fluid leak
  • Bad clutch
  • Damage to the idle control valve
  • Failing speed sensor
  • Bad spark plugs

To fix high RPMs in your car, you must figure out the exact cause and solve the problem. Your RPMs running high means your car’s engine works harder than necessary. You must figure out what’s causing it and choose the best solution for the problem.

Can new spark plugs increase horsepower?

Of course, new spark plugs increase horsepower and the overall performance of your car. New spark plugs ensure proper combustion and complete burn of a proper fuel-air mixture. This impacts the performance of your car’s engine and boosts horsepower.

The impact of new spark plugs on your horsepower does not mean that it will help your car break some speed record or start racing like you are in a fast and furious movie. The increase in horsepower by new spark plugs is usually in little percentages like 1 to 2%.

Your spark plugs act as a driving force to your car’s motion, but to achieve the best, you will need to use not just new spark plugs but the latest spark plug technology, the iridium spark plug technology.

Do high RPMs hurt the engine?

Yes, high RPMs hurt your engine until it eventually becomes damaged. The higher your RPMs go, the more pressure and force is mounted on your machine and its component.

Car manufacturers usually take cars on a road test to determine how extreme they can go on a high RPM. The impact of these tests tells a great toll on the car. When your car’s RPMs keep getting too high, your car will “throw a rod.”

This is a situation where your engine's connecting rod fractures, and the piston is thrown upward at an extremely fast rate (faster than the speed of sound), smashing through your engine’s cylinder head, destroying the valves.

The two-way damage can also pierce through the cylinder walls to damage your engine block.

This will extend to scalding steam, damage to your piston rings, and damaged gaskets, turbo, and the overall internal components of your car. High RPMs will hurt your engine and leave you spending tons of dollars on fixing them.

Can bad spark plugs cause RPMs to jump?

Yes, bad spark plugs can cause RPMs to jump. “RPM jumping,” referred to as fluctuations, is caused by bad spark plugs.

This usually happens when the spark plugs are damaged, dirty, or worn out, to the extent that they trigger vibrations and engine misfires in your car.

These vibrations and misfires caused by these bad spark plugs will cause your RPMs to jump.

Can spark plugs cause acceleration issues?

Yes, spark plugs cause acceleration issues, so your car will run rough at acceleration, run sluggishly and sometimes not accelerate at all.

You should check your spark plugs whenever you notice that your car’s acceleration is gradually reducing.

How many RPMs cause engine damage?

RPMs might vary for different engines, but the RPMs that causes engine damage is one that pushes within or beyond the red line on your tachometer.

Any RPM of about 5,000 will put stress on your engine. The damage might start from the piston, down to the cylinders, gradually breaking down the engine the more you rev higher.

You can look up your car’s user manual to decide the best torque, horsepower, and RPM suitable for you.


Bad spark plugs cause high RPMs, but they are not the only factors that can cause high RPMs. It would be best if you run a proper diagnosis.

You can hire the services of a professional to help you decide the exact cause of the high RPMs on your car and suggest the best solution to the problem.