As a car owner, noticing any signs of potential problems with your vehicle can be concerning. One issue that can cause significant anxiety is the presence of bad spark plugs. You may wonder about signs of bad spark plugs in Toyota Yaris (plus causes and solutions)
When spark plugs are worn or not functioning properly, they cause a decrease in fuel efficiency. This is because if the spark plugs are not functioning properly, the fuel will not burn as efficiently, leading to decreased fuel economy. Checking and replacing can not only improve fuel efficiency but also help prevent further damage to the engine.
It’s important to address the problem as soon as possible. Ignoring the signs of bad spark plugs leads to decreased performance, reduced fuel efficiency, and potentially even engine damage.
In this article, we’ll discuss some of the common signs of bad spark plugs in a Toyota Yaris, explore the causes, and provide some solutions to help you get your car running smoothly again.
What Are The Signs Of Bad Spark Plugs In Toyota Yaris?
There are several signs that indicate that the spark plugs in your Toyota Yaris are not functioning properly. Some of the most common signs of bad spark plugs include:

- Engine Misfire: Engine misfires or running rough is a sign that your spark plugs are not firing properly.
- Rough Idling: If you notice that your engine is idling roughly or the RPMs are fluctuating, it could be a sign that your spark plugs are not working as they should.
- Difficulty Starting: Trouble while starting could be a sign that your spark plugs are not providing the necessary spark to ignite the fuel in your engine.
- Poor Fuel Economy: Decreased fuel economy in your car is also a sign that your spark plugs are not functioning properly, causing your engine to work harder and burn more fuel.
- Lack Of Acceleration: If your car is slow to accelerate or feels sluggish, it indicates that your spark plugs are not firing correctly.
Causes Of Bad Spark Plugs In Toyota Yaris
Several possible causes of a bad spark plug in a Toyota Yaris are discussed below :
- Wear And Tear: Over time, spark plugs wear out and become dirty, corroded, or fouled. This leads to poor performance and eventual failure.
- Overheating: If the engine in your Toyota Yaris runs too hot, it causes the spark plugs to overheat and fail.
- Oil Contamination: Oil can seep into the spark plug wells and cause the plugs to fail, caused by worn gaskets or a damaged valve cover.
- Carbon Buildup: Carbon buildup on the spark plugs causes misfiring, poor fuel economy, and reduced performance.
- Improper Gap: If the spark plug gap is set incorrectly, it causes poor performance and misfiring.
- Low-Quality Or Wrong Spark Plugs: Using low-quality or the wrong spark plugs can also cause poor performance, misfiring, and engine damage.
Possible Fixes For Bad Spark Plugs In Toyota Yaris
Fixing bad spark plugs in a Toyota Yaris typically involves either cleaning, repairing, or replacing them. Here are some of the possible fixes that can help to address this issue:

- Cleaning: In some cases, spark plugs can be cleaned and re-gapped to restore their performance. This is typically done by a qualified mechanic with the tools and knowledge to do it correctly.
- Repairing: If the issue is caused by a faulty or damaged spark plug wire or ignition coil, replacing the faulty component help to solve the problem.
- Replacing: Severely worn, corroded, fouled, or damaged spark plugs they will need to be replaced. A qualified mechanic will recommend the best type of spark plug for your Yaris based on the manufacturer’s specifications and the driving conditions.
- Upgrading: If you frequently drive under harsh conditions, such as extreme temperatures or heavy loads, upgrading to high-performance spark plugs can improve the performance and lifespan of your spark plugs.
- Regular Maintenance: Regular maintenance, such as replacing the spark plugs on a schedule recommended by the manufacturer, helps to prevent spark plug issues from occurring in the first place.
How Often Do You Change Spark Plugs On A Yaris?
The recommended interval for changing spark plugs on a Toyota Yaris varies depending on the model year, the engine size, and the driving conditions. Generally, the manufacturer recommends changing spark plugs in a Toyota Yaris every 120,000 miles or eight years, whichever comes first.
However, it’s essential to consult the owner’s manual of your Toyota Yaris to get the manufacturer’s specific recommendations for your model. If you frequently drive under harsh conditions, such as high temperatures or dusty roads, you may need to change the spark plugs more frequently.
Similarly, if you notice any signs of bad spark plugs, such as misfiring, poor fuel economy, or difficulty starting, you may need to replace them before the recommended interval.
It’s important to stay on top of regular maintenance to keep your Toyota Yaris running smoothly and avoid more costly repairs down the road. If you have any questions or concerns about when to change the spark plugs on your Yaris, it’s always best to consult a qualified mechanic or dealership.
How Much Does It Cost To Change Spark Plugs In A Toyota Yaris?
The cost of replacing spark plugs in a Toyota Yaris can vary depending on the age and type of spark plugs used. Generally, spark plugs for a Toyota Yaris cost anywhere from $20 to $60 per spark plug, with labor costs ranging from $150 to $200.
The cost of replacing all four spark plugs in a Toyota Yaris can be anywhere from $140 to $420. Always try to find a quality mechanic with good knowledge of your vehicle type.
Conclusion
If you suspect your Toyota Crown spark plugs may be bad, the best way to confirm is to look at them directly. We hope after reading this article, you can now identify signs of bad spark plugs in Toyota Yaris (plus causes and solutions).
You can do this by removing the spark plugs from the engine and inspecting them for signs of damage or wear. If you find any signs of damage or wear, you likely need to replace the spark plugs.
Additionally, if you’re experiencing engine misfires or reduced fuel efficiency, this could indicate that the spark plugs are not functioning properly. It’s always best to consult with a professional mechanic if you’re unsure about any of the above.