Informational Guide

How Tight Should Spark Plugs Be?

In this guide, we answer how tight should spark plugs be and give you a guide for torque specs.

During your next automotive tune-up, you will want to know how to change spark plugs for superior engine performance. However, you might also be wondering how tight should spark plugs be?  

In this handy guide, we will answer how tight should spark plugs be tightened and help you figure out do you need to torque spark plugs? 

How tight should my spark plugs be? Without automotive spark plugs that are designed for your vehicle, the engine will not run properly. These plugs are required to provide the spark that ignites the air/fuel mixture in the combustion chamber. To ensure everything runs as it was designed, the spark plugs must be appropriately tightened in place. 

However, universal plugs aren’t available. For each car model, the build and diameter of the plugs will be different. It’s best to check the torque specs of the spark plugs you use to determine how tight they should be. For example, if you use Denso spark plugs, the manufacturer offers a torque chart you can follow.  

porsche engine with spark plugs

What Will Happen If Spark Plugs Are Too Loose?

Poor Engine Performance

Do I need to torque my spark plugs? Yes, because if they are too loose, you might start to experience engine misfires or have trouble getting the engine to accelerate. You might also notice issues starting the motor when the plugs are too loose.

Engine Pre-Ignition 

When the spark plugs are too loose, it leads to engine pre-ignition. This condition causes abnormal combustion as the fuel and air mixtures lights prematurely. Pre-ignition occurs when there is an ignition source aside from the spark, such as a hot spot in the chamber.  

Harmful Detonation

The pre-ignition of the loose spark plugs can also cause engine detonation that’s harmful. Spontaneous combustion occurring in the engine can create knocking and pinging, causing engine damage down the road. If left unchecked, the engine could fail completely.  

Dead Cylinder

When the spark plug becomes too loose within the cylinder, there’s the possibility that it could fall out. When this happens, it is known as a dead cylinder. The compression comes right out of the cylinder, causing severe engine performance issues that could lead to serious damage or an engine fire.  

cylinder on a gas engine

What Will Happen If Spark Plugs Are Too Tight?

Hard Or Impossible To Remove 

If you don’t know how much torque for spark plugs, you could overtighten it, making it more difficult, if not impossible, to remove later. The spark plug can become melded into the head of the cylinder with the corrosion and deposits acting like glue.

Damaged Cylinder Head 

If the cylinder bolt hole becomes stripped or deformed, you won’t be able to get another spark plug installed. In some cases, you might be able to drill out the hole to install a Helicoil repair. In other circumstances, replacing the cylinder head would be the only fix, which is expensive to perform.  

Foreign Objects In Combustion Chamber 

Do spark plugs need to be torqued to certain specs? Yes, because if they are overtightened, parts of the plug electrode or insulator could break off and fall into the combustion chamber. As these parts move around the engine, they lead to costly engine damage that cannot be repaired easily.  

Do Spark Plugs Need To Be Torqued? (How To Guide) 

Do you need a torque wrench for spark plugs? To get the spark plugs tightened appropriately, it’s best to have a torque wrench that shows you how much pressure has been applied. Here are some general steps you can follow when tightening spark plugs. 

  1. 1
    Find out the appropriate torque based on the type of spark plugs you are using and the vehicle you drive. You can find this information in your service manual. 
  2. 2
    Clean the spark plug hole to ensure there is no debris working against the installation.  
  3. 3
    Work with the engine cool.  
  4. 4
    Hand tighten all of the spark plugs until they are seated in the cylinder head.  
  5. 5
    With your torque wrench, turn the spark plugs to the appropriate measurement.  

If you aren’t sure how to torque the spark plugs properly, it’s best to get help from a qualified mechanic. It doesn’t cost much to get a professional automotive tune-up but can be extremely costly if you mess up the engine because of your inexperience.  

spark plug in an engine

How To Tighten Spark Plugs (Without A Torque Wrench)

Do I need a torque wrench to change spark plugs? If you don’t have a torque wrench, you can also tighten the spark plugs.  

  1. 1
    Clean the spark plug hole to ensure there is no debris working against the installation.  
  2. 2
    Work with the engine cool.  
  3. 3
    Hand tighten all of the spark plugs until they are seated in the cylinder head.  
  4. 4
    With a socket and ratchet, turn the 14mm and 18mm thread spark plugs a half turn to tighten.  
  5. 5
    If you are working with tapered plugs, tighten them with a 22.5° clockwise turn.  

People Also Ask (FAQs)

What would cause spark plugs to come loose? 

If there is debris in the hole, it can interfere with how the plug seats. At first, the plug might appear to be tightened, but the debris could loosen it over time, causing it to malfunction. They can also become loose due to a build-up of debris, so make sure you clean your spark plugs regularly.

Should you lubricate spark plug threads? 

Some people think that lubricant or anti-seize solutions are needed on the spark plugs, but the majority of manufacturers disagree. It’s okay to install spark plugs dry. Check with the manufacturer of your spark plugs to ensure you are following the recommendations.  

How do I stop my spark plugs from loosening?  

The best way to keep the spark plugs tightened is to figure out - do you need a torque wrench to change spark plugs? With a torque wrench and a clean cylinder hole, you can ensure the proper fit for your engine’s spark plugs.  

What does a failing spark plug sound like? 

If the spark plugs aren’t working correctly, you will start to notice engine performance issues, such as misfiring and rough idle, but there could also be noise associated with the problem. In some cases, faulty spark plugs lead to engine knocking.  


Do I need a torque wrench for spark plugs? It’s best to use a torque wrench to tighten the spark plugs according to factory specs. With the proper amount of torque applied, the engine can perform as it was intended.