Car Sputters After Getting Gas: Here Are Potential Solutions

Are you tired of coming to a stoplight and hearing your car sputter and cough after getting gas? It’s a common issue that many car owners experience, and it’s more than just a minor inconvenience. A car that sputters after getting gas can cause frustration, anxiety, and even potentially dangerous situations on the road. A lot of people assume that the gas they just put in their car is bad, but this isn’t always the case. In this article, we will discuss the various reasons why a car might sputter after getting gas, and how you can prevent it from happening again.

If your car sputters after getting gas, you might have a common issue with your EVAP system due to a loose gas cap. The EVAP system is an emissions control system that manages gasoline vapor from the fuel tank and prevents it from entering the atmosphere. One of the most common reasons why your car might sputter after getting gas is because the gas cap isn’t tightened properly or is missing completely. You should also check your fuel filter. If it is clogged, it can cause your car to sputter. Finally, you should check for any vacuum leaks. A vacuum leak can cause your car to sputter because it disrupts the flow of air and fuel to the engine. 

Bonus Read: Car won’t start after getting gas

What Exactly Is EVAP System?

The EVAP system, or Evaporative Emission Control System, is an important part of a vehicle’s emissions control system. This system is designed to capture and store fuel vapors that would otherwise escape into the atmosphere. It is an integral part of the vehicle’s air pollution control system, and is required to meet emission standards set by the Environmental Protection Agency (EPA). 

The EVAP system is made up of several components, including:

• Charcoal canister
• Purge valve
• Fuel tank pressure sensor
• Vent valve
• Gas cap of fuel tank 

The EVAP system works by routing vapor from the fuel tank and fuel lines into an activated charcoal canister. This canister is then used to trap the vapor and store it until the engine is running. When the vehicle is running, the stored vapor is then drawn into the engine and burned off along with the other air-fuel mixture. 

When the engine is running, the vent valve opens and air is sucked into the canister. This air helps to push the fuel vapors out of the canister and into the engine during the combustion process. The purge valve then opens, allowing the fuel vapors to be released into the engine.

The vent valve of EVAP system helps to prevent a vacuum from forming in the fuel tank. It allows fresh air to displace the fuel. The vent valve is opened all the time when the engine is running. The only time the ECU closes the canister vent is when it self-tests EVAP system for leaks. You’ll almost always find this vent valve bolted directly to the canister.

The ECU (engine control unit) only opens the purge valve when it interprets that there is excess of fuel vapors in the fuel tank. This signal is sent by the fuel tank pressure sensor installed on the fuel tank.

Why Was EVAP System Introduced In Engines?

EVAP system was introduced to allow fuel tank to breathe in and out without releasing fuel vapors into the atmosphere. Before EVAP system, there was a vent hole on fuel tank to prevent pressure and vacuum issues inside the fuel tank. But, it would also allow fuel vapors to directly escape into the atmosphere where they can combine with oxides of nitrogen, and produce harmful gases.

Now, you might be thinking why the fuel tank needs to breathe in and out. Your vehicle’s fuel tank needs to breathe in and out to prevent a process called cavitation, which can damage the fuel pump.

When the fuel pump sucks the fuel from fuel tank, it creates vacuum inside the tank. When a vacuum develops in the airspace above the fuel in the fuel tank, the fuel pump has to struggle against the vacuum to pump the fuel, and this can make maintaining fuel pressure difficult, starving the engine. 

If no air is inserted in a gas tank to replace the volume of fuel in the gas tank, it will develop a vacuum condition and your engine will starve. To prevent this from happening, the vent valve in EVAP system allows air to replace the fuel that was taken from the tank, and helps keep the pressure in the fuel tank at a steady level.   

Causes Of Car Sputtering After Getting Gas

Here are the causes of car sputtering after getting gas:

1. Gas Cap Is Not Properly Closed

After refueling your car, a loose gas cap is a common problem. Having loose gas cap seal will cause an EVAP to malfunction. It usually does not cause performance issues in your vehicle, but can trigger the check engine light if stays loose. A check engine light is triggered because the ECU interpretes that fuel vapors are leaking out of the fuel tank. This signal is sent by the fuel tank pressure sensor to the ECU.

However, if a gas cap stays loose for a long time, it can cause car to sputter. This is because gas caps are designed to seal the fuel tank, preventing fuel evaporation. When the gas cap is loose, it fails to seal EVAP system properly and fuel can evaporate. Furthermore, air from atmosphere casn suck into the fuel tank due to vacuum inside the tank. This in turn affects the air-fuel ratio, leading to a loss of power and your car sputtering.

How to fix?

Make sure that the seal of the gas cap is not cracked. You should tighten the gas gap until you hear 3 or 4 clicks. Also, check if there are deposits of carbon or dirt around the seal of the gas cap or around the fuel filler neck of your vehicle in which a gas cap is tightened. 

If there is dirt, debris and rust around gas cap and filler neck, you should clean it before putting the gas cap. You should also check is the seal/o-ring on the gas cap is not cracked. Make sure to lightly spray WD-40 over the o-ring seal of the gas cap. Make sure WD-40 spray does not dip over the seal.

You should also check if there is rust around the filler neck. If it is, lightly sand it with the sandpaper or steel brush. After that, apply a small amount of silicone grease to coat the ring of the filler neck to to help the fuel cap o-ring seal to the filler neck and prevent leaks.

2. Stuck EVAP Purge Valve

If you’ve ever fueled up your car at the gas station, and then experienced a sputtering or stalling engine shortly afterwards, it could be due to a stuck EVAP purge valve. 

The EVAP Purge Valve is responsible for releasing fuel vapors from the fuel tank back into the engine for combustion. This allows the fuel vapors to be burned off rather than released into the atmosphere. 

EVAP purge valve has solenoid, electronically controlled by the ECU. The ECU analyzes different operating parameters and decides when to open the EVAP purge valve.

If EVAP purge valve gets stuck open, excessive fuel vapors enter the engine’s air intake port. It causes an imbalance in the air to fuel ratio, which leads to a sputtering engine when you come to a stop.

How to spot?

EVAP purge valve is either located next to the throttle body of the engine or near the fuel tank under the vehicle. 

When it comes to troubleshooting a stuck EVAP Purge Valve, there are a multitude of potential culprits. The most frequently encountered cause is the accumulation of dirt, debris, or other foreign materials conglomerating inside the valve. 

Yet another factor that could be contributing to a stuck EVAP Purge Valve harkens back to issues with the solenoid. This crucial mechanism transmits an electrical current to the valve in order to trigger its opening and closing, but if it’s malfunctioning, this can interfere with the valve’s performance.

Here are the following steps to test EVAP purge valve:

• Turn off the ignition switch.
• Locate purge valve with the help of EVAP system diagram in owner’s manual
• Remove the purge valve
• Take a vacuum pump tester and connect it with the port on the purge valve that goes to the intake manifold of the engine.
• If the valve is not holding the vacuum, it means it is faulty.

The following video will help you a lot:

3. Blocked Charcoal Canister

The charcoal canister contains a bed of activated charcoal, which is designed to absorb and retain fuel vapors. This charcoal bed is not designed to hold liquid gasoline, only gasoline vapors.

The canister is connected to the fuel system and is usually located near the gas tank. When the engine is running, any excess fuel vapors are drawn into the canister, where they are stored until they are needed. 

When gas vapors are released during refueling, they are stored temporarily in the charcoal canister until they can be efficiently routed back into the engine and burned for fuel.

As cars age and gasoline becomes more volatile, the charcoal bed can become saturated with gas. When this happens, the tank is unable to breathe in, leading to the car sputtering after getting gas. 

In essence, if too much fuel vapors get into the charcoal canister, for example, by overfilling the gas tank, they can saturate the charcoal bed.  If the charcoal canister is full of fuel vapors, air can’t flow through it, which causes problems for the fuel system.

Air from outside the car must be able to flow into the gas tank as gasoline is burned by the engine. If the charcoal canister is full of gas, it won’t be able to absorb gasoline vapors anymore, and air won’t be able to flow through it.

When the tank is unable to “breathe in” because of the full charcoal canister, it causes an imbalanced pressure in the tank, which can result in problems such as a sputtering and stalling engine. This is because the engine is not getting the proper balance of fuel vapors and air to run smoothly.

How to spot?

Take out the charcoal canister, shake it and see if water, liquid fuel, or loose charcoal granules fall out. If yes, it means the charcoal canister is defective.

Using a flashlight, carefully inspect the exterior of the canister for any signs of damage, such as cracks or leaks. Additionally, inspect all hoses and connections of the charcoal canister for signs of wear, such as cracking or fraying.

You can also inspect charcoal canister by low-pressure compressed air into the one port of charocal canister, and see if air flows freely through the other port or not.

4. Damaged Vent Valve

The vent valve plays a crucial role in the EVAP system by allowing air to enter the system and preventing an overabundance of vacuum pressure inside the fuel tank. When the vent valve is closed, it will prevent air from entering the EVAP system, leading to an overabundance of vacuum pressure, which can lead to fuel starvation of the fuel pump. As a result, this can cause the car to experience a sputtering engine due to a lack of proper fuel supply.

How to spot?

To diagnose a canister vent valve is to connect it with the vacuum pump just as we do to test the EVAP purge valve. But for the canister vent valve, if the vacuum pump is not showing any vacuum, it means that the vent valve is healthy. If the pressure developed in the vent valve and it is being shown on the vacuum pump, it means that the vent valve is stuck closed.

For EVAP system to work properly, vent valve should remain open.

5. Kinks or Bends, Crack, Debris in the Fuel Vapor Hoses/Tubes

As a car owner, it can be particularly frustrating when your engine begins to sputter and stall after filling up at the gas station. One possible cause that is often overlooked is a problem with the Fuel Vapor Hoses/Tubes in the EVAP (Evaporative Emissions Control) system. These hoses and tubes are responsible for routing fuel vapors from your gas tank to the charcoal canister and back to the engine where they can be burned.

If these hoses or tubes become damaged, kinked, or blocked, it can cause issues with the proper regulation of fuel vapor flow. A kink or bend in the hose, for example, can restrict the flow of fuel vapor, leading to an imbalance in the air-to-fuel mixture required for stable engine running. 

This is because due to blockage in hoses, air couldn’t flow and fuel tank will not be able to breathe in and out.

How to spot?

To spot cracks in EVAP system hoses, you can use a UV light across the car’s underside, following the system’s path from the engine section to the rear fuel tank to inspect the EVAP system connections. Any smoke oozing from the system will lighten up in the ultraviolet light.

You might also need to perform a smoke test using a smoke machine to detect any leaks in EVAP hoses before proceeding further. For this, you can go to your nearby mechanic to have a professional smoke test done for the EVAP system.

To check the dirt or debris in the hoses, blow the air through them and see if there is some restriction that requires more force.

5. Bad Fuel Pump

A fuel pump is responsible for pumping fuel from the fuel tank to the engine, where it is then used to create the power needed to move the car. As you can imagine, if the fuel pump isn’t working correctly, then your car won’t be able to get the fuel it needs to create power. 

The reason why a bad fuel pump can cause your car to sputter after it has been filled up with gas is because of something called “vacuum in the air space”. When the fuel tank is unable to “breathe”, this vacuum will develop in the air space and this can cause the fuel pump to starve of fuel. 

How to spot?

Here is how to test fuel pump:

• Turn the ignition on
• Open the gas cap of the fuel tank
• If you do not hear the sound from the fuel tank, it could mean the fuel pump is not running
• Now, turn the ignition off
• If the fuel pump is running, you need to check fuel pressure using the fuel pump pressure test kit
• Locate the test port (Schrader valve) on the fuel line
• Fit down the hose of a pressure test kit on the test port
• If there is no fuel pressure on the test gauge, it means that the fuel pump needs to be replaced

6. Overfilling Of Fuel Tank

At first glance, it might seem like filling the fuel tank beyond capacity is a harmless mistake, but it can actually have serious consequences for your car’s performance. When we fill the fuel tank, we need to leave space for air to remain inside. This is because your car’s fuel system requires an air pocket to operate correctly.

When we overfill the gas tank beyond its recommended capacity, it can cause the EVAP (Evaporative Emission Control) canister to fill with fuel instead of vapor. The EVAP system is designed to collect and store fuel vapors that evaporate from the fuel tank. However, when we overfill the gas tank, fuel can enter the EVAP canister, leading to a malfunction in the system and causing the car to sputter and stall.

Additionally, overfilling can cause fuel to enter the sensors, vacuums, and solenoids in the EVAP system. This can cause their seals to dry off and become brittle, leading to sputtering when starting the car. In extreme cases, it can cause permanent damage to the sensors and solenoids.

How to fix?

Gas pumps use a mechanical linkage in the handle to sense the change in suction when gasoline in the tank rises high enough to block the hole. When the hole is blocked, the higher-pressure air closes a valve and halts the flow of gasoline. This is why the nozzle makes a “clunk” sound when the fuel tank is full.

So, to avoid overfilling, you can keep track of how much fuel goes into the tank, examine the fuel gauge, and remove the nozzle when the safety clicks off at the station.

Moreover, by revving the engine high, you can burn the excessive fuel in the tank, so it’s not overfilled anymore.

Some Of The Common EVAP System OBD2 Codes

• P0440: EVAP System Malfunction
• P0441: EVAP System Incorrect Purge Flow
• P0442: EVAP System Leak Detected (Small)
• P0443: EVAP System Purge Control Valve Circuit
• P0444: EVAP System Purge Control Valve Circuit Open
• P0445: EVAP System Purge Control Valve Circuit Shorted
• P0446: EVAP System Vent Control Circuit Malfunction
• P0447: EVAP System Vent Control Circuit Open
• P0448: EVAP System Vent Control Circuit Shorted
• P0449: EVAP System Vent Valve/Solenoid Circuit Malfunction
• P0450: EVAP System Pressure Sensor Malfunction
• P0451: EVAP System Pressure Sensor Range/Performance
• P0452: EVAP System Pressure Sensor Low Input
• P0453: EVAP System Pressure Sensor High Input
• P0454: EVAP System Pressure Sensor Intermittent
• P0455: EVAP System Leak Detected (Gross Leak)
• P0456: EVAP System Leak Detected (Very Small)

You can use OBD2 scan tool to check if there is any trouble code.