Engine sputtering clearly indicates something isn’t quite right under the hood. Sometimes, it may feel like the engine hesitates or struggles to maintain a smooth operation. Other times, it may feel like you won’t reach your destination at all. While it could be as simple as low gas, it could also mean you’re dealing with underlying issues ranging from mild to severe. But one thing is clear: it’s not something you want to ignore!
In this article, we cover the most common causes of engine sputtering and what you need to do to address the problem. We also highlight potential costs and end off by answering your top questions. Let’s get started!
What Causes Your Engine to Sputter?
Engine sputtering may occur in different situations. While it can be most evident when accelerating, it may also arise during idle or regular cruising.
Listed below are the most common causes of engine sputtering:
- Bad Spark Plugs
- Clogged Fuel Filter
- Bad Fuel Pump
- Vacuum Leak
- Dirty of Bad MAF Sensor
- Clogged Fuel Injectors
- Bad Catalytic Converter
- Bad Oxygen Sensor
Bad Spark Plugs
Bad spark plugs are considered one of the most common reasons for engine sputtering. Their role is to create the spark that ignites the air/fuel mixture, initiating the combustion process.
However, if the spark plugs become coated with carbon buildup or oil, they can struggle to produce this essential spark. The good news is that replacing spark plugs is usually relatively inexpensive, especially if you can handle the job yourself.
Note: Oil on the spark plugs can indicate an underlying issue, such as a leaky o-ring seal or damaged piston compression rings. If left unaddressed, this can lead to serious engine problems.
Clogged Fuel Filter
Secondly, we have the fuel filter. As its name suggests, the fuel filter removes impurities and contaminants from the fuel before it reaches the engine. This filter is part of your vehicle’s routine maintenance and should be replaced at regular intervals to prevent it from going bad.
If neglected, the filter can become clogged with debris, leading to restricted fuel flow to the engine. In extreme cases, this can cause the engine to stall or even prevent it from starting. Therefore, it’s wise to check when it was last replaced.
Bad Fuel Pump
The fuel in your gas tank doesn’t reach the engine by itself; it relies on the fuel pump. However, despite the fuel pump’s durable design and expected lifespan of 100,000 to 150,000 miles or more, it can fail like any mechanical component.
When the fuel pump fails, it can no longer deliver fuel to the engine as it should. Although there are many reasons for a fuel pump to go bad, continuously letting the tank empty and allowing the pump to suck up air or debris from the bottom can accelerate the wear.
A vacuum leak occurs when air enters the engine through a crack or hole in the intake manifold or vacuum hoses. This extra air disrupts the air/fuel mixture that the engine needs to run smoothly, causing the engine to sputter or hesitate.
The engine control unit (ECU) tries to compensate for the extra air by adjusting the fuel mixture, but it can only do so much. This sputtering sensation can be especially noticeable at idle or during acceleration.
Dirty Or Bad MAF Sensor
Despite their small size, the Mass Air Flow (MAF) sensor is crucial for smooth engine operation. Its job is to measure the air mass flowing into the engine intake and send this information to the engine control unit (ECU), which uses it to calculate the correct amount of fuel to inject into the engine.
If it’s bad or dirty, the sensor might not give accurate readings, leading to a lean or rich fuel mixture where the former likely causes your engine to starve and sputter.
Clogged Fuel Injectors
Your vehicle’s fuel injectors are responsible for delivering the precise amount of fuel to the engine’s combustion chamber, which the ECU determines. If the fuel injectors become clogged or malfunction, they can cause an uneven fuel flow and your engine to sputter.
In severe cases, this can cause your engine to stall or misfire, leading to further damage if left unaddressed.
Bad Catalytic Converter
A catalytic converter is an essential component of a vehicle’s exhaust system that helps to reduce harmful emissions. But despite its heroic efforts, it’s well-known for becoming clogged over time. When this happens, the exhaust gases cannot flow through the converter, causing back-pressure buildup in the exhaust system.
This can lead to jerky driving, as the engine struggles to expel exhaust gases and take in fresh air. The sputtering may be accompanied by a decrease in power and acceleration, as well as a decrease in fuel efficiency.
Bad Oxygen Sensor
The oxygen sensor, or the O2 sensor, measures the amount of oxygen in the exhaust gases and sends this information to the engine control unit (ECU). When working properly, it helps the ECU adjust the air-fuel mixture to achieve optimal combustion.
However, a faulty or failing oxygen sensor can and will likely provide inaccurate readings, leading to an improper air-fuel mixture. This can result in engine sputtering or misfiring.
List of Other Potential Causes
Listed above are some of the most common things that can cause your engine to sputter. But since these systems are complex and many things could cause the same symptom, we also wanted to highlight some of the less common ones as well:
- Damaged ignition coils
- Faulty throttle position sensor
- Bad fuel quality
- Malfunctioning ECU (Engine Control Unit)
- Worn timing belt
How to Diagnose and Fix a Sputtering Engine
The first step to fix a sputtering engine is to figure out what’s wrong. Here’s a step-by-step guide to help you with that:
A brief reminder about the importance of safety when working on vehicles. For instance, always ensure the vehicle is in park, using safety equipment like gloves and goggles, and working in a well-ventilated space.
Steps to Diagnosis:
Scan for Trouble Codes
Use a trouble code scanner, plug it into the OBD2 port that’s usually located beneath the dashboard on the driver’s side, and let it run a scan. It will provide you with any existing trouble codes, which can give hints or even directly point to the issue causing the sputtering.
If the scan shows several codes, you can reset them and take a short test drive to see which codes return. Write these codes down and reference them online or in your owner’s manual for specific insights.
Inspect Spark Plugs
With the engine off and cooled down, remove each spark plug and inspect for signs of wear, fouling, or damage. In some cases, you might be able to clean them with a spray-on cleaner and a wire brush. But if the spark plugs look worse for wear, it might be time to replace them.
If you recently replaced the spark plugs, consider if the wrong type was used. If so, it can cause engine performance issues.
Either way, replacing all spark plugs simultaneously is always good practice. And if you have copper spark plugs, you can consider choosing platinum or iridium spark plugs instead for a longer lifespan.
Check Fuel Pressure
Use a fuel pressure gauge to check if the pressure is within the recommended range specified in your owner’s manual. If the fuel pressure is too low or inconsistent, you must figure out where the issue lies. But it most certainly concerns the fuel pump, filter, or fuel injectors.
Check for a Vacuum Leak
Finding a vacuum leak is not always simple. Start by checking for any torn vacuum lines or disconnections. If you’re unsure where the vacuum lines are, you should be able to find a diagram in your service manual.
If there are no obvious signs, you can proceed by starting the engine and listen for any hissing sounds which might indicate a leak.
You can also use a smoke machine or an unlit propane torch. Without igniting it, run the tip along the vacuum lines and connections. As you do this, carefully listen to the engine’s RPM. If it spikes, there’s likely a leak. This could also work with a can of carb cleaner.
But be careful not to spray any surface that could ignite the carb cleaner or propane torch.
Clean the MAF Sensor
Find the MAF sensor typically located between the air filter and the engine’s intake manifold. With the engine off, cool, and keys out of the ignition, you can now remove the sensor from its bracket and clean it gently with an MAF sensor cleaner.
Let it completely dry before reinstalling it. Ensure you tighten the brackets. If the issues persist, consider replacing the sensor.
Seek Expert Assistance
Contacting a professional mechanic is probably best if you’ve gone through all the steps and still haven’t identified or resolved the issue. While DIY is rewarding, some problems require the expertise and equipment only professionals have.
How Much Does It Cost to Fix Engine Sputtering?
With so many possible causes, we understand that the cost of fixing the problem can be concerning. In this case, the repair and replacement cost can range from anywhere between $100 to $2,500 or more, depending on the reason your engine is sputtering and the vehicle you drive.
The most common causes of engine sputtering and their average estimated cost of repairs are listed below:
- Spark plugs: $80-$200
- Fuel filter: $100-$200
- Fuel pump: $800-$1,000
- Vacuum leak: $100-$1,000
- MAF sensor: $200-$400
- Oxygen sensor: $200-$400
- Fuel Injector: $400-$1,100
- Catalytic converter: $1,000-$2,500
Keep in mind that these are just average estimates, and the actual cost of repairs can vary depending on your vehicle make and model, the mechanic’s hourly rate, and the severity of the issue.
Frequently Asked Questions
What happens when your car sputters while driving?
When your car sputters while driving, it means that the engine is not achieving full combustion. This can be caused by various issues, such as a lack of fuel, dirty fuel injectors, failing spark plugs, or a loss of vacuum pressure. It can result in a rough-running engine, backfiring, and decreased power and performance.
What does a sputtering engine feel like?
A sputtering engine can feel like your car is jerking or hesitating while driving. You may also notice a loss of power or acceleration, and the engine may make unusual noises. These symptoms can be concerning and should be addressed as soon as possible to prevent further damage to your vehicle.
Is engine sputtering bad?
Engine sputtering is not necessarily bad, but it can be a symptom of various underlying issues, some of which can be serious. While it could be a simple problem like running out of gas, it could also indicate problems with the fuel system, exhaust system, or engine itself.
Is it safe to keep driving if my car is sputtering?
It is not recommended to continue driving your car if it is sputtering. This can be a sign of a serious issue that can cause further damage to your vehicle or even lead to a breakdown. It is best to pull over and have your car inspected by a qualified mechanic.
Can bad or low oil cause sputtering?
Bad or low oil levels may not directly cause sputtering but can contribute to engine problems such as misfiring. Worse than that, if the oil is contaminated or low enough, the engine won’t be lubricated as it needs and risk being severely damaged.
Can too much fuel cause sputtering?
Yes, too much fuel can cause sputtering. If the fuel mixture is too rich, meaning there is an excess of fuel compared to the amount of air, it can result in incomplete combustion and sputtering.
Is sputtering a misfire?
Sputtering is not necessarily a misfire. Sputtering can simply be a lack of power or delayed acceleration. However, a misfire can cause sputtering, and sputtering can sometimes turn into a misfire or backfire. When it does, the situation is much more alarming.
Engine sputtering indicates that your vehicle is not running at its best and may indicate various underlying issues. While some causes are more common than others, such as faulty spark plugs or a clogged fuel filter, the complexities of modern vehicles mean that the root of the problem could be any of a long list of potential culprits.
The costs of addressing engine sputtering vary widely, depending on the specific issue. However, given the potential for more significant damage if the problem is left unaddressed, it’s wise to act promptly.
For those comfortable with basic troubleshooting, this article provides a roadmap to identify and potentially rectify the problem. Yet, when in doubt, seeking the expertise of a professional mechanic is always a prudent choice. Above all, ensuring your vehicle’s safety and optimal performance should always be the top priority.