Can You Drive With Bad Spark Plugs?

  • by
can you drive with bad spark plugs

Sometimes you can forget to change the spark plugs. It happened to me also until one day the car did not start anymore. So if you’re wondering if can you drive with bad spark plugs, the answer is that it depends on the severity of the problem.

If the spark plug is not functioning at all is not recommended to drive with that faulty spark plug for a long time. Fuel that is traveling towards the evacuation system will damage the catalytic converter which can cause other critical issues. If the faulty spark plug is on its way to break, things like poor fuel economy, harsh idling and poor engine performance will arise.

Why does this matter?

What is a spark plug?

Think of the spark plugs as the porthole to look into the engine.

Depending on the number of cylinders that your car has, we define the number of spark plugs. The best example is when you have a four-cylinder you will have one per cylinder, meaning four spark plugs.

Spark plugs have a very important function for an engine. First, they are used for starting your engine, which is critical for normal vehicle behavior. Then the spark plugs ignite the mixture of fuel and air that it’s formed inside the cylinders to produce energy.

If you look at how they are built, you can define two electrodes that are separated by a gap. You can consider the air as the insulator between these electrodes. The spark plugs are connected to the ignition coils, which will provide a high voltage.

As the high voltage flows in the gap described above there will be a voltage drop. This voltage is arcing between the two electrodes and create a spark. Therefore, the created spark will ignite the fuel mixture inside the cylinder housing.

In your car manufacturer manual you can find details about the spark plugs that your car is using. Details like location, quantity and electrodes gap distance are available, so you will know exactly what tools or replacements we need.

Normally, the spark plugs have a lifetime of around 30k miles, but there are cases of better efficiency spark plugs that can work up to 100k miles.

Another important aspect is that you need to use exactly the type of spark plugs that are recommended for your car. If they equipped the vehicle with platinum or double platinum spark plugs it’s wise to use the same type.

Here’s something to remember

Can I drive with bad spark plugs?

That’s one of the most common questions for someone who’s asking if can you drive with bad spark plugs. There are some factors to consider and to check whether your issue is incipient or more advanced.

If you’re driving with a misfiring cylinder, critical problems can occur in your vehicle. By saying that, we need to think about what it means that one of the spark plugs in a cylinder is not working. Fuel will continue to be pumped in the cylinder, but no spark is present to ignite it.

That means the fuel will travel towards the evacuation system until it reaches the catalytic converter. Then, the catalytic converter gets polluted by the fuel. Here harmful effects can happen including catalytic converter melting and supra heating. Sometimes, the exhaust mechanism will get obstructed and in the worst-case scenario even catch fire, which will cause a disastrous situation.

In case the spark plug is not worn out, and it’s just on the point of breaking, several things can happen. Along with them, we can include:

1. Decreased fuel economy

This is usually because of the impact on the other cylinders and the fuel that’s not burnt. This will mess the car’s electronic control units that are pushing more fuel to keep up the pace. If the gap of the spark plug is not according to the manual, the air-fuel mixture will not burn accurately.

2. Low car performance

Again this is a sign that your spark plugs might be faulty. In a four cylinders engine, if one cylinder is misfiring the other three will have to work harder to maintain the performance. That’s not possible because they built the engine in a certain way and also can have a huge impact on the engine’s life.

Here you can examine the spark plugs and clean them. By doing this, it might be possible to extend their life until you will change them.

3. Difficulties in starting the engine

The vehicle startup system comprises multiple parts that need to function in harmony. If the spark plugs are bad, you will find it harder to start your car because you will not have a spark in one cylinder. In an internal combustion engine the spark is essential to move the cylinders. If the spark plugs are dirty or not functional it’s problematic to ensure this process.

4. Harsh idling or engine surging

When the vehicle is vibrating or running rough when idling, it might be a sign of bad spark plugs. Usually this can be easily detected if you know your car. You can check the sound that is making when the cylinder is misfiring when not driving, but the engine is on.

Another thing can happen when you are driving. It may seem like the car is not responding correctly to the way you are pressing on the gas pedal. Sometimes you can feel it’s lacking power, and sometimes you can feel extra power. This is because of the incorrect air-fuel mixture and the fact the spark is not present or not correctly timed.

You might also wonder:

Can you start a car without a spark plug?

Like we talked above, that will be very difficult. The engine needs the spark plugs to create the spark essential for the fuel to burn.

Although you can probably start it, that is not a good idea because you can provoke a lot of damage to other components. If you feel that your car is starting more difficult than usual, or not at all, it’s a good idea to check it first. There are other components involved in this process that can be faulty and you might point to the wrong one.


Whether or not you can drive with bad spark plugs, the best decision is not to do it, unless you cannot find other alternatives. It’s very important in a vehicle to have a good internal combustion process. Spark plugs play an important role and help your engine do run smooth and fluid.

When is the last time that you changed the spark plugs of your car? Maybe it’s time to do it.

Leave us your answer in the comments.



Leave a Reply

Your email address will not be published. Required fields are marked *