What Happens If Spark Plug Gap is Too Small? Real Answer!

You may have noticed your engine isn’t running smoothly or your fuel mileage has dropped. This might be because your spark plug gap is too small. A small spark plug gap means your engine can’t fire properly, leading to weak starts, low power, and wasted fuel. You don’t need to be a car expert to fix this. In this article, you’ll learn exactly what happens when the spark plug gap is too small, why it matters, and how to check and fix it easily.

Engine Starts Become Harder and Slower

When the gap in your spark plug is too small, your engine may not start quickly. You might turn the key and hear the engine crank, but it doesn’t fire up right away. That’s because the small gap creates a weak spark.

The spark needs to be strong enough to ignite the fuel and air mixture in the engine. If it’s not, the combustion doesn’t happen as it should. The engine then struggles to start or may not start at all in some cases.

This becomes a bigger problem in cold weather. Cold air makes fuel harder to burn. So, if your spark is already weak because the gap is too small, it will be even harder to start your engine when it’s cold. You might have to try several times before the engine turns over. This is frustrating and wastes time, especially when you’re in a hurry.

The spark plug’s job is simple — create a spark. But the spark has to be just right. When the gap is too small, it makes the spark weaker. This weak spark might still light the fuel, but not well enough. That’s why your engine hesitates during startup or might shake a little once it starts running. You may also notice it sounds different than usual, less smooth, more choppy.

Some people might think the battery or starter is the problem, but often it’s just the spark plug gap. A quick check and re-gap of the plugs can fix the issue and make starting the engine easy again.

• Engine cranks but doesn’t start easily
• Starting takes longer in cold weather
• Weak spark causes poor fuel ignition
• Engine may shake or hesitate after starting
• Often mistaken for battery or starter problem

Fuel Economy Drops and Wastes Money

Fuel economy is one of the first things that gets worse when the spark plug gap is too small. The spark isn’t strong enough to fully burn the air and fuel mixture inside the engine. When this happens, not all the fuel gets used. That means you’re paying for fuel that isn’t even helping your car run.

Normally, your engine is designed to get the most out of every drop of fuel. But with a weak spark, some fuel gets left behind. This unburned fuel either exits through the exhaust system or causes buildup inside the engine. Either way, it’s money down the drain. You’ll find yourself filling up the gas tank more often without driving any extra miles.

Also, if the spark plug gap is too small, the engine might not be able to adjust the fuel mixture correctly. Most modern cars have sensors that try to correct small problems by adjusting how much fuel is sent to the engine. But when the spark is too weak, even the sensors can’t fix the issue completely. As a result, the car uses more fuel to try to keep running smoothly.

You might not notice the drop in gas mileage right away. But over time, you’ll see a difference at the pump. If you used to drive 300 miles on a full tank, now it might only go 250 miles. That’s a big deal, especially with rising gas prices. Fixing the spark plug gap can bring back your normal fuel economy.

• Weak spark causes poor fuel burning
• More fuel used for same distance
• Gas tank empties faster than before
• Sensors can’t fully fix the problem
• Fuel gets wasted or causes carbon buildup

Engine Power Feels Low and Weak

One of the most noticeable effects of a small spark plug gap is the loss of power. You might press the gas pedal, but your car feels sluggish. It doesn’t respond as fast or pull as strong, especially when going uphill or trying to pass another car. This happens because the engine isn’t getting the power it should from the fuel.

The spark inside each cylinder is what creates the mini explosion that powers your engine. If the spark is weak, the explosion is smaller. That means less energy is created, and your car has to work harder to go the same speed. You’ll notice the car feels heavier or slower than usual.

Driving like this not only feels bad, but it’s also dangerous. Imagine needing to speed up quickly to avoid an accident or merge onto the highway, and your car doesn’t respond in time. That kind of delay can be risky. A proper spark plug gap helps make sure the engine delivers the power you need when you need it.

Also, the engine might make strange sounds when under load. If you’re towing something or driving with a full car, the engine will struggle more with a small gap. You might hear knocking, pinging, or feel vibration because the spark isn’t strong enough to handle the load.

• Slow acceleration when pressing gas
• Car feels heavy or slow
• Poor response during passing or merging
• Engine struggles under load
• Can be dangerous in traffic situations

Misfiring Happens Often While Driving

A small spark plug gap can lead to misfiring. Misfiring means the spark plug doesn’t ignite the fuel mixture properly. Instead of a smooth running engine, one or more cylinders fail to fire correctly. This causes shaking, jerking, or uneven driving.

You may feel the car hesitate or jerk, especially when going uphill or trying to speed up. Sometimes the check engine light will come on. Misfires can happen randomly or regularly depending on how small the gap is. It’s a sign that the combustion process is breaking down.

If this goes on for too long, it can lead to damage in other parts of the car. The catalytic converter can overheat from unburned fuel. The engine parts can wear out faster. Even your spark plugs will get dirty quicker and need replacing sooner than usual.

Misfires also make the car less enjoyable to drive. You don’t feel smooth acceleration. There may be loud sounds from the engine or exhaust. Fixing the spark plug gap can stop these misfires and bring back smooth driving.

• Engine jerks or hesitates
• Check engine light might appear
• Loud popping or knocking sounds
• Can damage catalytic converter
• Shortens life of spark plugs and engine parts

Emissions Increase and Engine Runs Dirty

When the spark plug gap is too small, the engine can’t burn fuel cleanly. This causes more pollution to come out of the exhaust. If your car needs to pass an emissions test, it might fail. The unburned fuel sends harmful gases like carbon monoxide into the air, which is bad for the environment and your health.

Besides that, the engine itself starts to get dirty. The carbon buildup from unburned fuel sticks to parts inside the engine. This makes it harder for the engine to run smoothly and can cause more long-term problems. It may even lead to engine knocking or overheating.

If you’re driving a car that pollutes more, you may also smell strong gas fumes when the engine is running. This is not only unpleasant but also dangerous if fumes get inside the car or garage. A proper spark plug gap helps keep the combustion clean and efficient, reducing emissions and keeping your engine in better shape.

• Car may fail emissions tests
• Engine produces more pollution
• Carbon builds up inside engine
• Gas fumes may be stronger
• Risk of engine damage increases

Spark Plugs Wear Out Faster Than Normal

When the gap is too small, spark plugs don’t work the way they’re supposed to. The spark is weak, and it has to work harder to keep the engine running. Over time, this extra work wears down the plugs faster than normal.

Normally, spark plugs can last tens of thousands of miles. But with a gap that’s too small, they might start to fail early. You may notice poor performance, misfiring, or bad fuel mileage sooner than expected. You’ll end up replacing them more often, which costs money and time.

Worn spark plugs can’t make a strong spark, which adds to the problem. It becomes a cycle — small gap causes weak spark, which causes wear, which causes even weaker spark. Checking and setting the correct gap before installing spark plugs can help avoid all of this.

• Spark plugs wear out quicker
• May need replacing earlier than expected
• Weak spark continues to get worse
• Costs more over time
• Cycle of poor performance continues

Final Thoughts

Keeping the spark plug gap right is one of the simplest ways to make sure your engine runs well. A gap that’s too small can cause hard starts, poor fuel economy, weak power, misfires, more pollution, and faster wear. It’s a small detail, but it makes a big difference. If you check and fix the spark plug gap when needed, you can avoid many of these problems and keep your car running better for longer.

Frequently Asked Questions (FAQs)

Is it bad to drive with a small spark plug gap?

Yes, driving with a small spark plug gap is not good for your engine. It can cause weak spark, which means your engine doesn’t run smoothly. You might feel your car shake, lose power, or burn more fuel than normal. Over time, it can damage parts like the catalytic converter or the spark plugs themselves. Fixing the gap is a simple thing that can prevent all these issues and help your car last longer.

Can a small spark plug gap cause misfire?

Yes, a small spark plug gap can cause misfires. The spark may not be strong enough to ignite the fuel inside the cylinder, which leads to misfiring. You’ll feel your engine jerk or stumble, especially when speeding up or going uphill. It might also cause the check engine light to come on. This is not only uncomfortable while driving but also bad for your engine if left unfixed.

Do I need a spark plug gap tool?

Yes, if you’re changing spark plugs, a gap tool is very helpful. It’s a small and cheap tool that lets you measure and adjust the gap to the correct size. Each car has a different spark plug gap recommendation. Without the tool, you can’t be sure the gap is right. Using the right tool helps your engine run better and makes sure the spark is strong.

Can too small a gap affect fuel mileage?

Yes, it definitely can. When the spark plug gap is too small, the fuel doesn’t burn completely. This means your engine has to use more fuel to do the same work. You’ll end up visiting the gas station more often. Your miles per gallon will drop, and you’ll spend more money on fuel even if your driving habits haven’t changed.

Is it easy to fix a small spark plug gap?

Yes, fixing the gap is pretty easy. You just need a gap measuring tool and something to gently widen the gap if needed. It takes just a few minutes per plug. You don’t need to be a car expert. Just find your car’s recommended gap size, check it with the tool, and adjust if necessary. It can make a big difference in how your engine performs.

Do I need to change spark plugs more often with a small gap?

Yes, if the gap is too small, the spark plugs wear out faster. They have to work harder to keep the engine running, which causes them to burn out sooner. You might have to replace them more often, which costs time and money. Keeping the gap correct helps the spark plugs last longer and keeps your engine happy.

Can emissions increase from a small spark plug gap?

Yes, a small spark plug gap can cause unburned fuel to leave the engine, leading to more pollution. This means your car could fail an emissions test. You may also notice the engine smells like gas or runs rough. Fixing the gap helps fuel burn cleaner and reduces pollution.

Is it safe to keep driving with a small gap in the spark plugs?

It’s not safe for the long term. While your car might still run, you’re risking damage to the engine and wasting fuel. The car won’t respond well when you need power, and it may misfire or stall. Fixing the spark plug gap is a small job that prevents bigger problems down the road.