Spark plugs have a precious metal that looks like a nipple. A spark jumps between that tip and a ground electrode overhead to ignite the air/fuel mixture. You want a strong spark to make as much contact with the air/fuel mixture as possible, making the combustion process efficient.
This is why the spark plug gap is so significant. It will either enhance or inhibit combustion. Mechanics associate the plug gap with the following variables:
- Fuel
The correct gap generates a dependable spark that improves fuel economy while reducing emissions. The wrong gap will send unburned fuel to the exhaust system. The result is higher emissions and poor fuel economy.
- Power
Does your engine’s power change whenever you switch spark plug brands? Spark plugs are usually pre-gapped. However, manufacturers don’t follow a particular gapping standard.
Therefore, don’t be surprised if the gaps in some spark plug brands are too wide while others are too small. Your engine will either run as expected because the gap is sufficient, or you will observe misfires and a disappointing power output.
- Ignition System
The wrong spark plug gap will strain the ignition system, forcing you to repair or replace coils, wires, distributor, and the like.
With those concerns in mind, what is the best spark plug gap? What is the appropriate response to the wrong spark plug gap? You will find the answers below:
What Happens If Plug Gap Is Too Wide/Narrow?
When you measure a spark plug gap, the readings will either exceed or fall below the recommendation in the manual. The consequences may vary depending on what you see:
Plug Gap Too Wide
- A wide gap is preferable because combustion is more efficient. You get a longer arc that does a better job of igniting the air-fuel mixture.
- You can improve an engine’s power and performance by widening the gap.
- However, a wide gap requires a higher voltage. This can strain the ignition system.
- Additionally, the wider the gap, the more difficult it becomes for the spark to consistently cross the distance. This can prevent the engine from starting.
- Turbulent combustion chambers can blow out weak sparks.
- Unfortunately, the plug gap becomes wider over time. You can’t prevent this outcome.
- Keep an eye on older plugs and replace or adjust them if the gap gets too wide.
Plug Gap Too Narrow
- A narrow gap allows the spark to jump between the electrodes with ease.
- A narrow gap will also produce a weak spark. The result is incomplete combustion.
- Some gaps are too small to ignite the air/fuel mixture.
What Is The Ideal Spark Plug Gap For My Specific Vehicle?
The standard gap for most vehicles is 0.028 – 0.060 inches
One spark plug gap cannot fit every vehicle. Different engines have different requirements.
Honda is 0.028 – 0.031, while Yamaha is 0.024 – 0.028. But do those slight differences matter? What if your vehicle falls outside the 0.028 – 0.060 range? Should it concern you?
Most consumers install new spark plugs without adjusting the gaps, yet their engines continue to function without incident. Modern vehicles are robust enough to tolerate diverse spark plug gaps. The ignition timing won’t change.
Problems only arise when the gap expands or narrows significantly. That can happen because of the following:
- The gap can shift during installation because you mishandled the spark plug.
- Excess heat can increase the gap.
- Factory errors can produce batches of plugs with the wrong gap.
A plug with the wrong gap will let you know via the reduced engine power, rough idling, frequent misfiring, poor acceleration, and various other symptoms. You can exacerbate these problems by modifying the engine and changing its gap requirements.
A pre-gapped spark plug is designed to work with standard engines. Modifications introduce variables manufacturers cannot account for.
How Can I Measure The Spark Plug Gap Accurately?
- Coin gap tools are a popular option because of their ease of use. You can stick one between a spark plug’s electrodes to measure the width. If you’ve never seen one, check the picture of a coin-style gap tool.
- Find the ramp on the coin and push the narrowest end into the gap. Rotate the coin until you detect resistance. Be gentle. You’re looking for a slight resistance. Record the measurements.
- While coin tools are adequate for older spark plugs, the new ones have tips made from precious metals. On the one hand, they have a higher melting point and greater resistance to wear. On the other hand, they are more fragile. Forcing a coin tool between the electrodes may break the tip.
- With that in mind, consider investing in a wire-type gauge. Wire and feeler tools are more accurate. You can even check the gap’s squareness and thickness.
- Check the manual for clarification. It may recommend a suitable measuring tool.
What Tools Can Be Used To Adjust The Spark Plug Gap?
Your response to a spark plug gap will depend on the measurements you record. If the gap is too wide, you will make it narrow. If the gap is too narrow, you will widen it. The tools and techniques people use vary. For instance, some mechanics use the gapping tool to pry narrow electrodes further apart.
You also have individuals that use screwdrivers. They will either pull on the electrode or gently tap it to narrow the gap. Others will knock the electrode against a hard surface. Autozone wants drivers to use the pre-drilled hole on the coil tool.
Insert the ground electrode through the hole and hook it on the rim of the gapper. Regardless of the method you use, you may damage the spark plug in the process. Keep in mind that adjustments of this sort take time.
You must measure the gap again and again while widening or narrowing the space between the electrodes until you replicate the measurements stated in the manual. Once you succeed, apply the following tips to maintain the correct gap:
- Perform regular maintenance. This prevents the engine from overheating. Excess heat can increase the spark plug gap.
- Hire a licensed and experienced expert to maintain the car. Laypeople can damage the spark plugs while installing them, making the gap narrower or wider.
- Measure the gaps of new spark plugs before installation. Don’t install spark plugs whose gaps are already too wide or too narrow. They will get even broader and thinner because of the engine’s poor performance and excess heat.
- Replace older plugs at the frequency the manual recommends. You should also consider replacing any plug you drop. Spark plugs are brittle. A significant fall can compromise them.
- If you’ve adjusted the gap, but symptoms like poor acceleration and high fuel consumption have persisted, you need new spark plugs.