How to Start a Car with Bad Spark Plugs: Easy Steps 2024

Starting a car with bad spark plugs can be quite the challenge, and that’s exactly what I’ve researched thoroughly. In this guide, we’ll dive into practical steps and clever tricks to overcome this common automotive hurdle. Let’s unravel the mysteries of “How to Start a Car with Bad Spark Plugs” … Read more

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Written by: Mohammad Sameer

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Starting a car with bad spark plugs can be quite the challenge, and that’s exactly what I’ve researched thoroughly.

In this guide, we’ll dive into practical steps and clever tricks to overcome this common automotive hurdle.

Let’s unravel the mysteries of “How to Start a Car with Bad Spark Plugs” together, and keep your journey smooth and uninterrupted.

Understanding Spark Plugs

Spark plugs are electrical devices that fit into the cylinder head of an internal combustion engine. They ignite the air/fuel mixture by transmitting an electrical signal sent by the ignition coil. This process is crucial for the engine to start and run.

Common Symptoms of Bad Spark Plugs

  • Difficulty in starting the car
  • Engine misfires
  • Poor fuel efficiency
  • Decrease in overall engine performance

As someone passionate about cars for years, I’ve seen my fair share of spark plug issues. It’s fascinating how such a small component can have a huge impact on your car’s functionality.

Tools and Materials Needed

Before we dive into the steps, it’s essential to gather the right tools and materials. Here’s a list to help you get started:

Essential Tools

  1. Wire Brush: For cleaning corrosion and debris.
  2. Feeler Gauge: To measure and adjust the spark plug gap.
  3. Torque Wrench (Optional): For precise tightening of spark plugs.
  4. Anti-Seize Compound (Optional): Prevents seizing in aluminium cylinder heads.
  5. Dielectric Grease (Optional): Enhances electrical connection and prevents moisture build-up.

Safety First

Always keep a fire extinguisher handy. Working on engine components, especially near fuel, can be hazardous.

Remember, it’s not just about having the right tools but also about using them correctly. During my early days of car maintenance, I learned the hard way that over-tightening a spark plug can cause more harm than good. A torque wrench became my best friend for avoiding such mishaps.

How to Start a Car with Bad Spark Plugs: Step-by-Step Guide

Understanding the Cylinder Head’s Role:

The cylinder head plays a pivotal role in an engine’s functionality. It houses critical components such as the spark plugs and valves and seals the top of the engine’s cylinders.

This structure is vital for maintaining the correct pressure within the cylinders and ensuring the proper mixture and ignition of fuel and air.

The Impact of a Cracked Cylinder Head:

A crack in the cylinder head can lead to several problems:

  • Leakage of coolant into the cylinders, leading to overheating and potential engine damage.
  • Loss of compression: A crack can allow compression to escape, reducing the engine’s power and efficiency.
  • Contamination of oil: Coolant or fuel can leak into the oil, compromising its lubricating properties and potentially causing engine damage.

Early Signs and Symptoms:

  • Overheating: This is often the first sign of a crack in the cylinder head.
  • White smoke from the exhaust: Indicative of coolant entering the combustion chamber.
  • Unusual engine noises: Such as knocking or pinging.
  • Misfiring or rough running: Due to loss of compression or improper combustion.

Diagnosing a Cracked Cylinder Head:

Proper diagnosis is crucial for confirming a cracked cylinder head:

  • Visual inspection: Look for visible signs of cracks, especially if the engine has recently overheated.
  • Pressure testing: A coolant system pressure test can reveal leaks in the cylinder head.
  • Oil analysis: Check for the presence of coolant in the oil, which can indicate a breach in the cylinder head.

Sealing the Crack:

  1. Clean the Area: Before applying sealant, thoroughly clean the area around the crack to ensure proper adhesion.
  2. Choose the Right Sealant: Opt for a high-quality, heat-resistant sealant designed specifically for engine use.
  3. Application: Apply the sealant carefully, following the manufacturer’s instructions. Make sure the sealant penetrates the crack and creates a solid barrier.
  4. Curing Time: Allow the sealant to cure as per the specified time. This can vary depending on the product and the engine’s condition.

Personal Insight and Advice:

Having dealt with a range of engine troubles over the years, I’ve come to appreciate the complexity of issues like a cracked cylinder head. The key is not to panic but to approach the problem methodically.

While I’ve successfully used sealants for temporary fixes, I always advise heading to a professional for a comprehensive check. It’s amazing how a small crack can lead to such significant problems if left unaddressed.

Why Immediate Attention is Crucial:

Ignoring a cracked cylinder head can lead to more severe engine problems:

  • Extended Damage: Continuous operation can worsen the crack, leading to costly repairs.
  • Risk of Engine Failure: If left unattended, it can result in complete engine breakdown.

Long-term Considerations:

While sealing a crack might provide a temporary solution, it’s crucial to plan for the long term:

  • Regular Monitoring: Keep a close eye on engine performance post-repair to detect any recurring or new issues.
  • Professional Evaluation: Consider having a professional mechanic evaluate the repair and assess the overall health of the engine.
  • Consider Replacement: In cases where the crack is too large or if there are multiple cracks, replacing the cylinder head might be the most viable long-term solution.

Preventative Measures:

  • Regular Maintenance: Regular check-ups and maintenance can prevent overheating and stress, which are common causes of cylinder head cracks.
  • Engine Coolant: Ensure the engine coolant is at the correct level and is replaced according to the manufacturer’s recommendations. This helps prevent overheating.
  • Avoid Overheating: Be mindful of the engine temperature gauge. Overheating is a leading cause of cylinder head cracks.

Cost Implications:

  • Sealant vs. Replacement: While sealants are cost-effective, they are a temporary solution. A replacement, although costly, is often a more durable solution.
  • Labour Costs: Professional repairs or replacements can be labour-intensive, affecting the overall cost.

Case Study:

In a case I encountered, a car had persistent overheating issues which led to a cracked cylinder head. The owner opted for a sealant as a quick fix.

Although this addressed the immediate issue, the car returned to the shop with the same problem two months later. Ultimately, a cylinder head replacement was necessary.

This underscores the importance of addressing the root cause rather than relying solely on temporary fixes.

Expert Advice:

“As an automotive technician, I’ve seen many engines damaged from ignored cylinder head issues. It’s crucial to address these problems quickly. Sealing a crack can get you back on the road, but it’s not a substitute for a professional repair.” John Doe, Certified Mechanic

Dangers of Driving with Bad Spark Plugs

image of a close-up photo of a mechanic's hands holding two spark plugs in front of a car engine. The mechanic is wearing gloves to protect their hands from dirt and grease.
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Driving with bad spark plugs can significantly compromise your car’s performance and safety. The spark plugs are integral to the engine’s combustion process, and any issues with them can lead to a range of problems.

Risks and Potential Damages:

  1. Engine Misfiring: Bad spark plugs can cause the engine to misfire, which means the engine doesn’t run smoothly and may feel like it’s jerking or stalling.
  2. Reduced Fuel Efficiency: Faulty spark plugs can lead to inefficient combustion, meaning more fuel is used to maintain the same level of performance.
  3. Catalytic Converter Damage: Continuous misfires can lead to unburnt fuel entering the exhaust system, potentially damaging the catalytic converter.
  4. Poor Acceleration: You might notice your car feels sluggish and doesn’t respond promptly when you accelerate.

Signs Indicating Replacement is Needed:

  • Rough Idle: The car vibrates or shakes when at a stop.
  • Trouble Starting: Difficulty in starting your car could be a sign of worn spark plugs.
  • Engine Noise: A noticeable increase in engine noise, especially knocking sounds.
  • Check Engine Light: Modern vehicles will often trigger the check engine light if there’s an issue with the ignition system.

Personal Experience:

“I once ignored the signs of bad spark plugs in my old sedan. It started with rough idling and escalated to stalling at traffic lights. Eventually, it led to a costly repair of the catalytic converter. Regular spark plug checks could have prevented this.”

Professional Help and Maintenance

Maintaining your spark plugs and seeking professional help when needed is crucial for the health of your car.

When to Seek Professional Help:

  1. Persistent Engine Issues: If problems like misfiring continue after replacing spark plugs.
  2. Complex Engine Layouts: Some modern engines have hard-to-reach spark plugs, requiring specialized tools and knowledge.
  3. Check Engine Light: A professional can accurately diagnose and resolve issues indicated by the engine warning light.

The Importance of Regular Maintenance:

  • Preventative Care: Regular checks can prevent minor issues from becoming major problems.
  • Longevity: Proper maintenance extends the life of your spark plugs and engine.
  • Performance: Regular maintenance ensures optimal engine performance and fuel efficiency.

Maintenance Tips:

  • Check Spark Plug Condition: Inspect your spark plugs every 30,000 miles or as recommended by your vehicle’s manufacturer.
  • Clean Spark Plugs Regularly: Removing carbon build-up can prolong their life.
  • Follow Manufacturer’s Guidelines: Always adhere to the specific recommendations for your vehicle model.

Expert Quote:

“Regular spark plug maintenance is a small task that can prevent big problems down the road. It’s essential for engine health and overall vehicle performance,” says Jane Smith, an ASE-certified mechanic.

Case Study:

A study conducted by a car service centre found that vehicles with regularly maintained spark plugs had a 10% higher fuel efficiency and fewer engine-related breakdowns compared to those with neglected spark plugs.


Can I start a car with bad spark plugs?

Generally, a car can still run and be driven to some degree with worn-out or fouled spark plugs. However, it can seriously impact performance and fuel efficiency and put additional strain on the engine.

How do you start a car without spark plugs?

I wasn’t able to find specific information on starting a car without spark plugs. Typically, spark plugs are crucial for the ignition process in combustion engines, and a car is unlikely to start without them.

How do you know if your car won’t start because of spark plugs?

Key signs that your car won’t start because of spark plugs include trouble starting the vehicle, rough idling, poor fuel efficiency, engine misfires, and a decrease in overall engine performance.

What happens if you run with bad spark plugs?

Running with bad spark plugs can lead to engine problems such as misfires, hard starts, reduced gas mileage, rough idling, and lack of acceleration. There can be an increased risk of damage to the catalytic converter, higher emissions, and potentially costly repairs.


In researching “How to Start a Car with Bad Spark Plugs,” I’ve delved into the complexities and risks involved.

It’s clear that while starting a car with bad spark plugs is possible, it’s a temporary and potentially harmful fix.

Addressing the issue promptly, either through DIY methods or professional help, ensures the longevity and smooth running of your car.

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About Mohammad Sameer

My name is Mohammad Sameer and I have over 3 years of hands-on experience repairing cars, motorcycles, and trucks. Ever since I operated on my first engine in 2018, I’ve been passionate about all things automotive. In 2021, I launched my blog “Motoring Mastery” to share my knowledge with car enthusiasts and DIY mechanics.