How To Gap Spark Plugs Without A Tool? (+3 FAQs)

Your spark plug gap is responsible for the electric spark that ignites the air fuel mixture. As a result, an incorrect spark gap leads to misfiring, spark plug fouling, and other issues. 

So what is the best gapping tool for spark plugs?
And how do you gap spark plugs without tool?

In this article, we’ll expllain how to gap spark plugs without a tool. We’ll also examine why they need a proper gap, the consequences of an incorrect spark gap, and the best tools for gapping a new spark plug.

This Article Contains: 

• How To Gap Spark Plugs Without Tool (Step-By-Step)
• 3 Spark Plug Gap FAQs
  • Why Do Spark Plugs Need To Be Gapped?
  • What Is The Best Tool For Gapping Spark Plugs?
  • What Are The Consequences Of Incorrectly Gapped Spark Plugs?

Let’s get started!

How To Gap Spark Plugs Without Tool (Step-By-Step)

Maintaining the spark plug gap is an important part of keeping your old spark plug healthy and running smoothly. Ideally, you should use the right tool for gapping your spark plugs. But in case you don’t have any spark plug gap tool on hand, here’s how you can achieve the correct gap. 

Things you’ll need: 

• Manufacturer’s manual
• Coins (penny, dime) 
• Screwdriver

Note: Before you roll up your sleeves and get started with the gap adjustment, remember to be gentle with the spark plug electrode tip. It can break very easily and cause serious engine damage. 

If you’re not confident in your mechanical skills, it’s best to let your mechanic handle the repairs. 

With that out of the way, here is how you can gap spark plugs without a tool: 

1. Start by using a torque wrench to loosen the old spark plug. You can use a socket wrench, but a torque wrench is also helpful when installing new plug sets.

2. Remove the spark plug from the ignition system. Be careful not to damage the spark plug wire or the ignition coil. 

3. Identify the recommended gap for your car’s spark plugs. These are typically defined in the manufacturer’s manual.

4. Next, compare the recommended gap to your coin’s size. For reference, a penny measures 0.06” while a dime is 0.053”. If your recommended gap size is different from these two, you’ll likely need to get a spark plug gap gauge or gapping tool. 

5. If the coin fits within the recommended specification, you can use it as a gapper. Start by gently sliding the coin between the spark plug gap. Check to see if the gap measurement aligns with the spark plug gap setting.

6. For a bigger gap, you can use the back end of a screwdriver to bend the ground electrode (ground strap) inwards gently. 

7. If you have a very narrow gap, you can carefully use the coin to push the ground electrode outwards. 

8. Be very gentle. Be careful not to touch the center electrode tip. 

9. Your spark plug gap should be within the correct gap parameters. If not, it’s probably best to use a spark plug gapping tool or consult a mechanic.

This method is not recommended for expensive platinum or iridium spark plugs. Iridium spark plugs can be very delicate and can bend very easily with too much pressure, thus damaging the plugs.

Note: When installing a new plug, make sure you use a torque wrench to tighten the new spark plug into the cylinder head. Be careful with the spark plug wire and ignition coil.

Keeping this in mind, what are some other things you should know about spark plugs? 

3 Spark Plug Gap FAQs

Here are some frequently asked questions about the spark plug gap and their answers.

1. Why Do Spark Plugs Need To Be Gapped? 

Spark plugs are fine-tuned pieces of equipment and are very delicate to handle. The spark plug gap plays a major role in the functioning of the spark plugs. 

If you have a narrow gap, your spark plugs will generate an inefficient or weak spark and lead to lower fuel efficiency and engine performance. 

If you have a bigger gap, the sparks won’t consistently ‘jump’ across the distance between the ground electrode and center electrode. This could lead to a rough idling engine, reduced fuel economy, or worse, engine failure. 

So, regular inspection and gapping are important for maintaining an old spark plug.

Note: A new plug is mostly likely pre-gapped within the correct gap specifications. But you should always check the gap specification against a new spark plug set. 

2. What Is The Best Tool For Gapping Spark Plugs?

While you can gap spark plugs with household items in some situations, most technicians and car mechanics strongly recommend using a spark plug gapping tool.

When gapping spark plugs, your mechanic will use industry-approved tools (a gapper) that do not damage the spark plugs (mainly the center electrode). 

These could be a:

• Feeler Gap Gauge — A feeler gauge is a gap tool that consists of well-calibrated metal strips of varying thickness parameters. It typically looks like a pocket knife and is a very handy and inexpensive gapper. 

• Coin Gap Gauge — A coin gauge or a ramp-style gap tool appears similar to a silver dollar coin with markings along the edges. The outermost edge is the thinnest, and it keeps increasing in width for bigger gap measurements, as you move towards the middle of the tool.
  
  These are the easiest to use in DIYs since they don’t damage the spark plug electrode. However, they can be quite expensive compared to others and easily bend or scrape.

• Wire-Loop Style Gap Gauge — A wire-loop spark plug gapping tool looks like a silver dollar with several wire loops of varying thicknesses attached to the outer edge. It may also contain a hook for gap adjustment. 

3. What Are The Consequences Of Incorrectly Gapped Spark Plugs?

If your spark plugs do not have the proper gap configuration, they may cause damage to the ignition system, cylinder head, and other car parts.

An incorrect gap size can lead to a range of problems, including:

• Engine misfire
• Rough idling
• Spark plug fouling
• Knocking or clicking sounds from the engine
• Poor engine performance
• Engine stalling
• Difficulty starting the car

Apart from these, a lack of a proper gap can also lead to poor acceleration and engine failure.