A car that hesitates after filling the gas tank usually indicates a problem with the fuel system. But not always. My wife and I have felt a light but perceptible shutter every time we fill our Ford Fiesta and Toyota Corolla with gas.
The most common reason why a car struggles to start after filling it with gas is due to a bad purge valve.
But for a proper diagnosis, you’ll want to take your car to a certified specialist that will be able to identify exactly what’s causing your car to hesitate after fill up. For now, here are a few possibilities.
1. Bad Purge Valve
One major reason why your car hesitates after filling the gas tank could be the purge valve. Also known as a fuel vent valve, a purge valve removes excess fuel vapor from a vehicle’s evaporative emission control system.
Typically located in the fuel tank, it opens to allow fuel vapor to be drawn into the engine where it’s burned rather than released into the atmosphere as pollution.
A bad purge valve can cause rough idling which could be the hesitation you feel. The rough idling can be accompanied by a check engine light.
One of the primary reasons for a faulty purge valve is bad wiring or wiring that’s degraded over time causing the purge valve to malfunction.
2. Bad EGR Valve
The exhaust gas recirculation (EGR) valve is another crucial component to the exhaust system that could cause hesitation.
The EGR valve is a part of the engine management system with a similar job to the purge valve. If it’s clogged with carbon, it won’t be able to operate correctly causing sputtering and hesitation.
An EGR valve recirculates finely metered quantities of exhaust gas to the engine intake system to increase efficiency, reduce fuel consumption and lower NOx emissions. But instead of being near the gas tank, an EGR valve is located in the engine between the exhaust and intake manifold.
3. Weak Battery
A weak battery can have an indirect impact on engine performance causing your car to hesitate after filling the gas tank. The alternator and fuel pump can both be affected by a weak battery. The fuel pump helps gasoline travel from the gas tank to the engine. Its ability to function is tied to the battery’s efficiency.
A weak battery means there’s not enough amperage to start the vehicle. Or if it does start, the fuel pump can’t process gasoline at a high enough rate. Leading to lean fuel issues that cause hesitation. That with other factors can also lead to engine misfires which might be the hesitation you feel.
4. Using Low Quality Fuel
It is so important to pump your car with the right grade of octane for the best engine performance. Fuel with insufficient octane reduces combustion which will cause an engine to hesitate. I had an Eagle Talon with a turbocharged engine which I lent to a friend back in high school.
He accidentally filled the tank with low grade fuel. When he brought the car back to me, it would hesitate every time I start it up; or start moving from a standstill; or try to accelerate. This happened until all the low-grade gasoline left the system. Mercifully, no engine lights came on and there didn’t appear to be any permanent damage.
5. Contaminated Fuel
You may not feel the effects of contaminated fuel when you first start your car. But you’ll definitely feel it when you accelerate. In some cases of contaminated fuel, the car won’t respond at all when you press the accelerator.
Or the car might drop speed suddenly and pick up speed just as quickly. One of the most common contaminants of engine fuel is water. This can affect both the engine compression and combustion which are necessary for any kind of movement from your ride.
If your gas cap can’t seal the gas tank, water will easily enter the tank while you’re washing your car or while driving through rain.
6. Issues with the Starter
Another reason why your car hesitates after filling the gas tank may have nothing to do with the gas or the tank at all. The issue could be coming from a bad starter.
A starter motor gives an engine its initial turn so that the combustion cycle can begin. Once the combustion cycle begins, the engine will keep running under its own power. A starter motor requires a lot of electricity to accomplish this task. You can listen for a starter motor that’s beginning to go bad.
Other than your engine hesitating to turn over, other symptoms include a clicking or grinding noise when you twist the ignition key or push the start button. Either way, you’ll want to get this checked out as soon as possible before your starter stops working altogether.
7. Faulty Sensors
If your car hesitates after filling the gas tank, the problem could be due to a failed oxygen sensor. If one of the oxygen (O2) sensors in your exhaust has failed. The ECU won’t be able to monitor emissions properly and pressure may drop, which causes the hesitation or bucking that you’re feeling.
This happened to my Nissan Maxima when I was in college. The check engine light came on and the hesitations got so bad one day that I had to go straight to a mechanic instead of school and work.
Hesitation is the result of too much air in the combustion chamber. Similarly, too much fuel can cause the engine to surge as the RPMs climb higher and higher.
8. Faulty Solenoids
Another reason why your car hesitates after filling the gas tank that isn’t obvious is the transmission. Also called a cylinoid, a failed solenoid can result in transmission slippage causing your car to hesitate.
A solenoid operates deeply submerged in transmission fluid. It’s an electro-hydraulic valve that controls fluid flow into and throughout an automatic transmission.
Solenoids can fail primarily due to the consistent hot and cold cycling in the harsh environment of a transmission. They can also fail for mechanical reasons. Or just wear out over time. This is why regular transmission service is important.
9. Spark Plug Issues
Spark plugs are part of the ignition system. They’re necessary for giving the pistons the power they need to keep your car moving forward. But if one or more spark plugs are faulty. They’ll have trouble creating enough spark for the ignition processes in an engine. Rough starts, hesitation and poor acceleration are all common symptoms of a bad spark plug.
I experienced this issue in a Dodge Stealth I owned. The spark plugs were old and covered in residue from burning air and fuel that formed deposits and built up on the spark plug’s center and side electrodes. The result was that they had a hard time providing the spark the engine needed to move. The hesitation was most apparent every time I tried to accelerate.
10. Clogged Fuel Filter
Under heavy loads, like accelerating onto a freeway from a standstill. A clogged fuel filter can cause your engine to hesitate.
The fuel filter is part of an engine’s fuel supply system. It acts as a permeable barrier for cleaning gasoline of impurities, sediments, contaminants and rust before the gasoline can get into the injection system.
Most vehicles have two fuel filters: one in the fuel tank and one in the fuel line. Contaminants that get past a clogged fuel filter can cause all sorts of damage to an engine. So, it’s important to get this looked at as soon as possible.
11. Failing Fuel Pump
If the fuel pump can’t send enough fuel into the combustion chamber, your engine will show signs of hesitation. A failing fuel pump can also cause surging which is when it sends too much fuel into the combustion chamber. The result is a car that picks up speed in spurts.
A fuel pump that’s starting to fail will make loud whining sounds that’s audible from the gas tank. It can also make this noise if you’re low on fuel or if the fuel is contaminated in some way.
12. Damaged Fuel Injector Lines
Fuel injector lines are the rubber hoses that connect the injectors to the rest of the engine. They’re similar to fuel hoses since they’re also responsible for transporting fuel around an engine. Fuel injector lines are under a great deal of pressure from the fuel injection system (upward of 50 PSI).
While damaged fuel injector lines aren’t incredibly common, you can find them in older engines with higher miles. Another obvious sign of issues with fuel injector lines, besides performance, is the smell of fuel which indicates leaky injector lines.
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