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how tight should spark plugs be

How Tight Should Spark Plugs Be? Beginner’s Instruction

Spark plugs play an essential role in igniting the car’s engine. Therefore, the selection, installation, and repair also require professionalism and care.

Usually, when repairs are complex, you should take them to the experts. If you need to screw or reinstall a simple spark plug, you can completely do it yourself at home.

However, not everyone understands how tight spark plugs should be. So this article will help you better understand the job and how to do it.

How Tight Should Spark Plugs Be?

If your vehicle has an iron cylinder head, you can install the spark plug manually with a new copper washer. Then you continue to twist the wrench until there is resistance and add ¼ – ½ turns to tighten.

However, today’s developments allow vehicles to use more aluminum cylinder heads. It means that if you screw the spark plug too tight, the spark plug starter will be completely damaged and need to be replaced with a new one.

As such, you should use a torque wrench and follow the manufacturer’s instructions and be careful in tightening the spark plugs. Some situations can happen when you do the work:

Where to use a torque wrench:

You must read the manufacturer’s manual carefully, as different manufacturers will have various torque recommendations. Entering the spark plug number in the search box will make it easier to find the torque setting. Then it would help if you did as in the instructions.

Where there is no torque wrench:

You can tighten the spark plug with your fingers and continue tightening with a plug wrench when you don’t have the equipment to do it. Here are some prominent brands that you might end up using: Autolite, NGK, Bosch, Champion, Denso, E3. In which each product has different uses, you can refer to the source from the supplier.

how tight should my spark plugs be

Spark Plugs Tightening Process

Tightening the spark plug is simple, but it needs the most precision and care. Otherwise, your car will encounter some complex problems. Before that, you must disconnect the spark plugs, determine the order and location of disassembly or assembly. Here are the steps to tighten spark plugs for you:

  • Step 1: The first thing in drawing the spark plug is to clean the surroundings and the details, avoiding dirt and damage. There are two popular cleaning methods: Abrasives and A Blowtorch.
  • Step 2: After you make sure to clean all the residue and dust on the device, use your hand to turn the spark plug back until you feel resistance. When the cylinder head hits the force pad, it’s a sign that you need to move on to the next step.
  • Step 3: You use torque, torque wrench, or not to tighten the spark plug. Please note that torque specifications vary by different suppliers. Alternatively, you can also use a spark plug wrench to draw it.
  • Step 4: Finally, reconnect the spark plug wire or the ignition coil to the plug. At the same time, the tightening of the spark plugs is finished, and your car is ready to go.


What happens if spark plugs are not tight enough?

If you screw the spark plug too loosely, it will cause the device to slide from its original position on top of the cylinder. Thus, the spark plug area in contact with the cylinder head is not enough to transfer heat. Moreover, the combustion chamber causes overheating, pre-ignition, and even dangerous detonation.

What happens if spark plugs are too loose?

In contrast to the above case, when you tighten the spark plug too tightly, it will damage the threads in the cylinder head and the spark plug thread. At the same time, the gasket inside the spark plug gets stressed and damages the product’s insulator.

What does a bad spark plug look like?

If you have a bad spark plug and need to replace it, it will show some signs of working poor, not working, or using more fuel.

When the ignition system malfunctions, the car’s acceleration takes place more slowly, it can also come from worn-out spark plugs due to long-term operation. If the vehicle is experiencing poor fuel economy, it may be due to the incorrect spacing between the spark plug electrodes and can be repaired. Conversely, if the cause comes from corrosion, you need to replace the product with a new one.

Some other cases, such as engine deviation, cause erratic tripping or jerking noises. You should check the sensor, spark plug wire, or spark plug connector to the wire. If you continue to drive in this situation, it will increase emissions, reduce power, and save fuel.

Besides, due to corroded spark plugs, your car may have Engine Surging or Hesitating or difficult to start.

Why do I smell gas after changing spark plugs?

In case you smell unpleasant gas or smoke after replacing the spark plugs. You should check the newly installed part because it is most likely coming from this location.

The spark plugs may not have been tightened properly, which could cause smoke to leak into the car’s combustion chamber. The unit near the HVAC inlet is the leading cause of the gas smell you’ve noticed.

The test includes: Remove each spark plug and rechecking each coil carefully. If you find anything uncertain, use a wrench and re-tighten the spark plugs. The gas smell will disappear after the safety details, thanks to the tightening of the spark plug.

However, if this condition continues to occur, you need to bring the vehicle to a repair shop for a closer inspection and replacement.


Thus, the article has given instructions for installing spark plugs in the most detail. We hope you will use it correctly for your device.

A faulty part will lead to a system failure because they are all interconnected. Therefore, you should check the engine, tires, and other details of the car regularly; it will help you be safer when moving.

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