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Home / Symptoms / Engine Sputtering

Four common causes for the vehicle engine sputtering and their related parts.

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Is Your Car's Engine Sputtering?

The engine is sputtering because of a faulty fuel pump or mechanical failure, causing the unmeasured fuel pressure to create sputters. But it can also be because of worn spark plugs, faulty sensors, or a damaged ignition coil.

In addition, some issues related to engine sputtering can prevent your car from starting, leaving you stranded and in a dangerous predicament.

The good news is that engine sputtering is easy to recognize and more straightforward to identify when the "check engine" light comes on. If you take your car to a technician before the problem damages the engine, the fix could be as simple as replacing the spark plugs or cleaning the fuel pump. Unfortunately, putting the issue on hold can severely impact your car's fuel efficiency.

Watch out: A sputtering engine relates to how your car intakes and burns fuel. If it doesn't burn fuel cleanly and efficiently, your fuel economy suffers, risking expensive repairs to your engine, exhaust system, and catalytic converter. Plus, your car creates excess emissions that damage the environment.

The most common causes of the car’s engine sputtering

The most common causes for a car’s engine sputtering:

Faulty fuel pump: The fuel pump uses a motor to push fuel, increasing hydraulic pressure and ensuring the fluid reaches the engine at the right time. However, if the fuel pump is faulty, the system’s hydraulic pressure gets lower and the fluid struggles to reach the engine properly. Consequently, the engine starts struggling with low fuel amount, causing misfires and sputtering.
Dirty mass airflow sensor: The mass airflow sensor measures the amount of air going into the engine, it’s an airflow component that prevents the engine from overheating. However, if this sensor is faulty, your vehicle loses track of how much air goes to the engine, resulting in combustion issues and overheating since the engine needs to operate with knowledge of the current airflow.
Restricted catalytic converter: The catalytic converter is a “box” that processes the gases and vapors the engine releases, making them less toxic, and filtering out their impurities before releasing them into the environment. However, if the catalytic converter gets clogged, these gas and vapors struggle to pass through it, building up, overheating the engine, and resulting in combustion issues and sputtering.
Dirty fuel injectors: The fuel injectors work directly inside the engine by spraying fuel into it to keep the combustion process going. However, if the fuel injectors fail by either spraying too much fuel or too little, the combustion process gets bad, resulting in misfires and sputtering.
Worn spark plugs: Spark plugs are components inside the engine that ignite the air-fuel mixture in the combustion chamber by creating a small electric spark. This spark causes a mini-explosion when contacting the fuel that powers the engine. However, when spark plugs fail, these sparks might lose rhythm or time, resulting in engine misfires and sputtering.
Ignition coil failing: The ignition coil is an electrical component in the engine that transforms low-voltage battery power (12 volts) into the high voltage (thousands of volts) needed to create a strong electric spark at the spark plugs. It basically acts as a transformer that strengthens the vehicle’s voltage. However, if the coil fails, this electrical spark might become weak, uneven, and out of rhythm, resulting in engine misfires and sputtering.

Frequently Asked Questions

Has your fuel economy been gradually decreasing?

You may also experience a rough idle or the check engine light on. Wear on your spark plugs directly affects your car's fuel economy.

The electrodes in a spark plug become corroded and separated from each other after years of use. While this micro-millimeter separation isn't apparent on the tiny electrodes, it often causes obvious tell-tale signs, such as decreased gas mileage, engine sputtering, and a sulphuric odor from the unburned fuel.
Are your RPMs fluctuating while your car is idling?

You may also experience the check engine light flashing or vehicle hesitation during acceleration.

If your fuel injectors are dirty or damaged, they lose their ability to effectively break down fuel and inject it into their corresponding engine cylinders. Properly atomized fuel burns completely, providing maximum power to the pistons and crankshaft that keep your engine spinning. A disruption to this process can cause the engine to chug and the "check engine" light to come on. In addition, the cylinders with dirty fuel injectors won't contribute as much power to the engine's crankshaft, which results in fluctuations in the engine's RPMs. These fluctuations are more evident while your vehicle is idling.
Does your exhaust smell like sulfur or rotten eggs?

You may also experience a rough engine at idle and notice the check engine light is on.

A catalytic converter that functions correctly converts the emissions from fuel combustion into water vapor in your exhaust. The unconverted emissions will cause a noticeable smell if the catalytic fails.
Is your vehicle cranking longer than usual before starting?

You may also experience a rough idle or the check engine light on. Your fuel pump could be failing.

This pump inside the fuel tank is supposed to send fuel to your engine at the proper pressure and volume to get it started and keep it operating while your vehicle is running. The fuel pump keeps the pressure even when your car isn't running, so your engine is always ready to start. If it malfunctions, your engine might crank long before it starts. Listen for any extra noise. That delay before starting is the fuel pump building pressure once more.
Is your check engine light flashing?

You may also experience a loss of fuel economy or vibrations and jerking while driving.

The engine control computer monitors your ignition coil to ensure it generates enough voltage to burn fuel thoroughly. Suppose a cylinder's coil isn't contributing to the process. In that case, the computer senses this and knows that significant quantities of unburned fuel go through the catalytic converter and into the exhaust. You can sometimes smell this wasted fuel and feel disruptions in the engine's running. This unburned fuel will damage the catalytic converter in short order. When an ignition coil fails to generate high voltage, the car's computer warns you by flashing the check engine light during this ignition misfire.
Is your check engine light steadily lit?

You may also experience a loss of fuel economy or vibrations and jerking while driving.

Your engine needs both fuel and air to burn it to generate power. That's where the mass airflow sensor comes in. This sensor measures the air coming into the engine to calculate the proper amount of fuel to inject to maximize the vehicle's fuel economy. If the sensor wires on this instrument get dirty, it will no longer give accurate readings, and the fuel-to-air ratio in the engine will be unbalanced. If the vehicle's computer senses an odd amount of air compared to the space in the throttle, the check engine light will activate, and the engine won't run as smoothly as it should.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Dirty fuel injector

The most common reason for a car’s engine sputtering is due to dirty fuel injectors. Fuel injectors are essential combustion components and work to deliver fuel so the engine can combust. These injectors spray fuel in the combustion chamber at a proper time and rhythm to supply the engine’s demands. However, if these injectors are faulty they’ll cause fuel flow issues in the engine, affecting the combustion process and resulting in misfires and sputtering.

Symptoms it causes: Apart from the sputtering engine you might notice engine misfires, rough idling, engine stalling, lawnmower noises, etc.
High risk of priority: A clogged fuel injector can’t provide the needed fuel for the vehicle’s combustion process, leading to engine problems and causing lower performance and high fuel consumption. In the worst cases, the engine might suffer major damage and breakdown.

How exactly do fuel injectors get dirty?

Fuel injectors get naturally dirty over time due to carbon deposits on their spraying end. This happens expectedly since fuel is constantly pushing through the spraying end and leaving deposits there. Therefore, regular maintenance is vital to ensure these injectors are clean; it’s advisable to clean fuel injectors every 30,000 miles.

Go safe: Ask for a mechanic to inspect your vehicle’s combustion system to investigate if the fuel injectors are dirty due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the fuel injectors to become dirty. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a dirty fuel injector service

A combustion system inspection is the most transparent process to understand why your vehicle’s fuel injector is dirty. This is because many components surrounding the fuel injector and combustion chamber can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a dirty fuel injector and solve an engine sputtering issue.

A customer dropped off their vehicle after noticing that the RPM gauge bounced around while idling. The customer also notified the shop that the "check engine" light had been on for weeks.

The technician took a test drive and noticed that the check engine light was on, and the engine felt like it was misfiring at idle. The technician ran a vehicle health inspection and found a code indicating a misfire on cylinder number four.

After the additional diagnostics were authorized, the technician used a dedicated vehicle-specific scanner and found a high rate of misfires on the cylinder. The technician removed the number four spark plug and found significant raw fuel on the electrode. The spark plug on cylinder number three looked normal with minimal wear.

The technician checked the cylinder compression on numbers 3 and 4 and found they were within manufacturer specifications and 2% of each other. After switching the spark plugs and coils of the two cylinders, the technician restarted the vehicle to check for live misfires on the scanner and found that they stayed with cylinder four. The technician then removed the fuel injectors for those cylinders and found significant debris on both tips. After switching the injectors on three and four and restarting the vehicle, they found that the misfire was now on cylinder number 3, thus proving that the injector now in number 3 was the problem.

The technician performed a fuel injector cleaning service authorized by the customer. After the injector cleaning service and clearing the codes, the technician found no remaining misfires on any cylinders.

Dirty fuel injectors

In this case, the mechanic put the “Immediate Action” tag on the fuel injector.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for weird braking from a vehicle and their related parts.

Is Your Car's Engine Sputtering?

The most common causes of the car’s engine sputtering

Frequently Asked Questions

Has your fuel economy been gradually decreasing?

Are your RPMs fluctuating while your car is idling?

Does your exhaust smell like sulfur or rotten eggs?

Is your vehicle cranking longer than usual before starting?

Is your check engine light flashing?

Is your check engine light steadily lit?

Typical fixes to address the cause(s)

The most common cause: Dirty fuel injector

How exactly do fuel injectors get dirty?

Transparency example in a dirty fuel injector service

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