Spark Plug Won’t Go In All The Way: Easy Fix in 4 Steps

What can you do if your spark plug won’t go in all the way in your car? It can be quite frustrating because the car won’t start without a spark plug. We share below how to fix it.

If you are new to car mechanics, you might not know the exact purpose of spark plugs and plug threads. However, this tiny component gets your engine started, and damage to this could mean a great deal of trouble.

There are times when the spark plug needs changing, and you see that the plug needs to go into its socket fully. What then? Let us tell you something about how spark plugs work and how you can fix them if there is a problem with fitting.

Spark Plug Won't Go In All The Way

How Are Spark Plugs Important In A Car?

Spark plugs are the components that are installed in a car’s engine to provide a spark that will fuel up the engine.

These simple plugs have a couple of threads inside and are directly attached to the engine, helping it produce power. The spark plugs emit a spark between two arcs that lets the fuel and air mixture get the engine running.

Why Do Spark Plugs Not Go In All The Way?

Spark plugs are tiny components that have to fit in the socket carefully for it to work. Unfortunately, this is a delicate job, and the plug might not go in for many reasons. In any situation, it is important to install and remove a spark plug carefully, so there is no major problem over time.

Here are the most common reasons that your spark plug is not going all the way into the socket:

  • The plug has not been installed properly into the engine
  • The threads in your spark plugs are not clean and have to be cleaned out
  • If the plug has been removed incorrectly, causing damage to the plug socket
  • If you are installing the wrong plug, which is not compatible with your car’s engine

Besides all these, you need the right equipment, especially the plug wires and torque wrench, to carry out the whole process of removing or installing the spark plug.

Spark Plug Won't Go In All The Way

How To Remove A Spark Plug Correctly?

Sometimes, the main problem people face with installing spark plugs is that the earlier plug needs to be removed properly. Spark plug sockets are usually very sensitive, and it might take some experience to carefully remove one before installing a new one.

If you are trying your hand at removing a spark plug correctly, here are the important steps that you need to keep in mind.

Locate the spark plug

Locating the spark plug is the first thing you need to do. It is located in a cylindrical hole in the engine. There is a wire connected to the spark plug boot – that can be pulled off with one end. Make sure you are not tugging at it or pulling it too quickly, which can damage the whole plug.

Use a Torque Wrench

Once you have removed the wire, use a torque wrench to remove the spark plug hole. Use a spark plug attachment and turn it counterclockwise, which can easily unscrew the plug. If the plug is too tight or somehow stuck, ensure you do not pull at any of the wires, or you may sever it.

Check the old plug

Once you have removed the spark plug, inspect it closely. If it has been in the car for too long, the spark plug will be black and dirty at one end. The plug wires could also be severed, which may be the main reason the plug is not working anymore.

Check the threads

When you have removed the spark plug, make sure to check the engine threads as well as the spark plug threads to figure out the problem. If the threads in the engine are dirty, clean them up with a solution.

If you have bought a used car whose previous owners were not careful about maintenance, you can be in trouble with the spark plug. This is why it is recommended that you get the car checked out early on by a professional to install a new spark plug safely and properly.

Threading The Spark Plug

Rethreading or reattaching a spark plug has to be done with special equipment because this is a sensitive component that could be damaged easily. To clean the spark plug wires caught up together, you need to use a thread chaser to separate them.

A spark plug thread chaser is used to clear out all the threads in the spark plug socket. You need to insert the thread chaser into the socket and align the wires by cleaning them individually. This usually takes out the dirt stuck between the threads.

The only problem with using a thread is that some of the residues from the cleaning can go back into the engine and cause additional problems.

Spark Plug Won't Go In All The Way

How Frequently Do You Need To Change Spark Plugs?

Your car’s model, the type of spark plug you have installed, and maintenance of your car – these are the first things you need to consider before changing your spark plug. Sometimes, you need to look out for the signs of spark plug damage that will help you replace the plug before it is completely worn out.

Some of the common signs of spark plug damage can be:

  • Struggle to start your engine
  • If your car is going to a rough idle frequently
  • There is increased fuel consumption
  • The acceleration in your car may become slow

These can be the first signs of a problem with your spark plug. The only way to ensure you are fine with the spark plug mid-journey is to inspect the plug during regular maintenance. Make sure that you are checking for wear and tear and also the position of the plug in the engine.

Frequently Asked Questions

What happens if a spark plug isn’t all the way in?

If a spark plug is not installed fully into the socket or is not tightened properly, it can cause engine damage. A spark because of a loose spark plug can cause the cylinder head to be blown out, which leaves the engine exposed. It could also lead to pre-ignition that is harmful to the engine.

Spark Plug Won't Go In All The Way

Can you spray WD-40 in the spark plug hole?

It is not a good idea to spray WD-40 in a spark plug hole. Firstly, it is not a good lubricant that can be used on car engines. Secondly, WD-40 can work as a solvent that washes off the oil on the cylinder walls, which can harm the car engine.

Should spark plugs be really tight?

Spark plugs should be tightened between 8-40nm, in line with the torque settings recommended by the manufacturers. You should check for the socket type and wrench that you are using. Too much strain on the spark plug is not good for the engine in the long run.

Why does my spark plug keep popping out?

If a spark plug is installed incorrectly, a little space can create a lot of combustion gases that create pressure on the cylinder and pop the plug wire. There can also be air pockets that create heat, expanding the wire and popping out the plug.

Spark Plug Won't Go In All The Way


For any kind of component in a car’s engine, there have to be several things taken into account. The tiniest disturbance damages the car’s engine in its surrounding components, so you must take extra care when dealing with them.

Finally, we suggest that if there is a problem with the internal parts of the car, just pay a visit to your mechanic to avoid a major problem.

Thank you for reading!

Photo of author

Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

Leave a Comment