Your car hesitates when accelerating from a stop is a frustratingly visible problem that can pop up at any time. When you press down on the gas pedal to go forward, you will experience the power being cut off for a few seconds before the vehicle moves. Instead of moving faster, the speed is decreased. The vehicle might even stumble for a few seconds. What happens when your car hesitates when accelerating from a stop?
Having to stop at a red light or parking anywhere other than your home garage can make you super anxious. Not only is this particular issue annoying, but it can also be dangerous. The person in the vehicle behind you will have no idea about the jerking issues you are facing. Thus, making the entire situation embarrassing as well as risky.
The majority of the time, if a car hesitates when accelerating from a stop, the culprit is either dirty fuel injectors or a blocked fuel intake. However, there are quite a few extra reasons which may be contributing to the issue.
- How Does A Car Engine Work?
- Common Reasons & Causes Why
- Diagnosis & Troubleshooting
- Accelerating At Low Speeds
- Accelerating At High Speeds
- Fixing & Repair Costs
How Does A Car Engine Work
Combustion engines (both gas and diesel) in vehicles need an exact blend of air and fuel to run smoothly. If the mixture is contaminated in any way, the engine may run too rich (not adequate fuel). Or, too lean (not enough air). If a car hesitates when accelerating from a stop, the engine is most likely dealing with an air/fuel blend that is too lean.
Engines that are not functioning to their full potential will start displaying symptoms such as hesitation. Unfortunately, it deteriorates with time. If you see any signs such as stuttering in your vehicle. And no matter what hour of the ride it is during, you have to get that checked immediately.
Car Hesitates When Accelerating
In the simplest words, hesitation or delay of the engine when accelerating happens if the engine does not receive enough power, and requires additional power to accelerate from a halt than keeping the speed of a moving car.
The engine produces power by making combustions in the combustion chamber. The “materials” needed for these explosions are fuel and air. When mixed in an optimal ratio, the two create an ignition started by the spark plug. There are multiple cylinders in the engine, and ignitions take place inside these cylinders in a repetitive order so there is a continuous energy supply to the engine for it to operate.
Thus, if there is any problem with the engine components controlling the mechanism for combusting the airflow and fuel supply, the engine fails to get enough power for the process. As a result, the car hesitates when accelerating from a stop.
The reasons behind this issue can form a rather long list. Examine the following components in order when the car hesitates when accelerating from stop:
Car Hesitates When Accelerating From Stop, Reasons #1: The Air Filter
One of the most common reasons behind a car that stutters when accelerating from a stop, and fortunately, one of the easier ones to repair, is a polluted air filter. A vehicle’s engine needs a constant air supply to run, and that part of the equation can be negatively affected by a dirty and clogged air filter. Burdened by dust buildup, the necessary component of the vehicle stops functioning properly.
A clogged air filter stops the engine from getting the air needed by the combustion chamber to generate sparks. If not repaired for a prolonged period, this small issue can smother the engine, reducing fuel economy while increasing the risks of driving.
To solve this issue, however, all you have to do is remove the air filter from its designated air box, check and replace it with a new one.
Car Hesitates When Accelerating From Stop, Reasons #2: Mass Airflow Sensor
The mass airflow sensor is the next component to check after you have decided that the air filter is not the cause of the issues. This component is tasked with keeping track of the air volume entering the engine and reporting the data to the Engine Control Unit, or ECU. The computer uses this information to determine the remaining fuel to be delivered by the fuel injectors.
A stuck or failing sensor gives the wrong information, stopping the engine from getting the correct amount of fuel. As a response, the engine produces suboptimal energy and causes the car to hesitate when driving uphill or accelerating from a stop. Keep in mind that if the reason is the mass airflow sensor, it might or might not set off a trigger code.
Car Hesitates When Accelerating From Stop, Reasons #3: Fuel Pump
While the engine requires fuel and air to be injected into the chamber, the fuel tank stores fuel. A fuel pump, which is also called a fuel transfer pump, is required to transfer diesel or gasoline to the engine from the fuel tank, particularly to the fuel injectors or carburetors before dispersing fuel into the chamber.
Therefore, it goes without saying that with a faulty fuel pump, the vehicle does not get the correct volume of fuel at any given time, and performance is hampered. A damaged or dirty fuel pump causes the engine to not get enough fuel to generate energy and consequently, the car hesitates when accelerating from a stop.
Car Hesitates When Accelerating From Stop, Reasons #4: Fuel Injectors
Once the engine receives the fuel from the fuel pump, the fuel injectors spritz fuel inside the cylinder. After that, the fuel gets combined with air at a fixed ratio and the spark plug creates a “spark.” Similar to the fuel pump and air filter, the fuel injector may also accumulate sludge and dirt over time, which negatively affects its ability to supply the right amount of fuel for the process of combustion.
Therefore, the engine does not have enough resources to produce energy for a smooth powering up.
Car Hesitates When Accelerating From Stop, Reasons #5: Fuel Filter
The fuel filter suffers from a similar tendency as the air filter – it can get clogged or dirty. The problem can cause a loss of power, sometimes even a no-start state, as the engine does not get adequate fuel for optimal performance. Suboptimal engine performance also results in poor fuel economy.
In most newer vehicles, the fuel filter can be found in the fuel tank. Take the vehicle to a mechanic if you are not familiar with handling things like that. If the vehicle comes with an external fuel filter, replacing it is somewhat straightforward and cheap.
Car Hesitates When Accelerating From Stop, Reasons #6: Accelerator Pump
If you ride an old car with a carburetor, it should most definitely have an accelerator pump. A faulty accelerator pump in need of repair can be why the car hesitates when accelerating from a stop. There is a plunger rod in there with a rubber seal piston that spritzes a little raw gas inside the carburetor. With fuel and air mixing inside, the engine is prompted to be more responsive to the accelerator.
When the seal wears out, it transfers a huge volume of air with not enough gas to the cylinder. The car starts hesitating when you hit the accelerator from a stop position. The pump has to be replaced to solve this problem, along with replacing or cleaning the fuel filter.
Car Hesitates When Accelerating From Stop, Reasons #7: Throttle Position Sensor
The throttle position sensor is an important part of any vehicle’s throttle body system. You can find it between the air filter and the intake manifold of the engine. The throttle position sensor makes sure the engine is getting the right volume of fuel and air for optimal combustion.
Every time you step on the gas pedal, the butterfly valve inside turns to release a specific amount of air into the engine’s intake manifold and the engine. As the pedal is pressed farther in, the throttle butterfly valve opens more.
Simultaneously, the throttle position sensor transmits signals to the ECU to report the condition of the throttle butterfly valve. The ECU takes that information to modify the amount of fuel the chamber needs at any specific time, making the perfect conditions for the ignitions to take place.
Car Hesitates When Accelerating From Stop, Reasons #8: Malfunctioned Throttle Position Sensor
Like any other component of the vehicle, the throttle position sensor is prone to malfunction. Its mechanical parts wear out with time and need replacement. Left unattended for too long, the malfunctioning throttle position sensor starts relaying the wrong information to the computer.
There are a handful of other symptoms to keep an eye out for which will confirm that the throttle position sensor is at fault. In most conditions, if there is a problem with the throttle sensor, the CEL (Check Engine Light) will be illuminated. Moreover, most automobile makers add a “limp home” mode of operation which is a mode where the vehicle runs on decreased power. This is triggered if there is a problem with the engine. Thanks to this new feature, drivers can get off crowded highways safer.
If a malfunctioning position sensor is an answer to why your car hesitates when accelerating from a stop, get it inspected as soon as possible. An engine that is not receiving the right fuel-air ratio for optimal function is working below-preferred efficiency. Apart from lowering fuel economy, this condition will also damage the engine, decreasing its lifespan.
Car Hesitates When Accelerating From Stop, Reasons #9: Exhaust Gas Recirculation (EGR) Valve
An Exhaust Gas Recirculation valve, as its name suggests, recirculates exhaust created during the combustion process in the engine into the cycle to be reutilized. Thus, it reduces the temperature inside and lowers the generation of toxic nitrous oxide. EGR valves open and close and control the flow of gas in the process.
Over time, a thick and hard wall of carbon is built up around it, locking the closing and opening mechanism of the EGR. This, in return, blocks the system passage and forces incorrect data into the ECU. The ECU fails to calculate the right amount of fuel and air to be injected into the chamber, causing delayed acceleration in the long run.
A faulty or stuck EGR valve can also raise carbon emissions as well as the temperature of the engine. Keep in mind that a heated engine will not perform to its fullest potential or last too long. A problem like this eats away at the lifespan of an engine. You may also notice decreased mileage. That’s why car makers recommend inspecting the EGR passages and valves every 50,000 miles.
Car Hesitates When Accelerating From Stop, Reasons #10: Coil Pack
Cars made from the year 2000 onward have special engines. These engines are equipped with a developed pack of ignition coils. Sitting on top of the spark plugs, these coils directly fire the plug. The ECU electronically controls these coil packs. In comparison to the conventional firing mechanism that needs an ignition coil, plug wires, and mechanical distributor, coil packs generally make a stronger and hotter spark, which produces better horsepower and combustion in a vehicle’s engine.
Needless to say, a poor coil pack affects the firing capacity of spark plugs, therefore impeding combustion and ignition. The engine cannot generate enough power and the car starts to stall when acceleration stops. In addition, you can experience a rough-running state and a stumbling engine. Luckily, coil packs are easy to find and change, generally requiring only a screwdriver or small nut driver.
Car Hesitates When Accelerating From Stop, Reasons #11: Oxygen Sensor
Oxygen content inside the car has to be maintained at all times for optimal operation. The job of the O2 sensors or oxygen sensors is to observe the oxygen amount of the exhaust alongside the other gases. Once it sends this information to the engine control unit, the computer can make better fuel-metering and emissions-control decisions. The component can be found in the exhaust stream, normally with one close to the exhaust manifold and the other lower down the exhaust pipe.
So, the information from the oxygen sensor plays an essential role in accurate engine timing, proper air to fuel ratio, and combustion intervals. So, a faulty O2 sensor can throw off the fuel calculation to fuel delivery, making the engine run too rich.
Little to no air reaches the engine and it reacts by not generating enough power for smooth acceleration. Another sign of a poor O2 sensor is a strong gasoline smell, particularly when idling, as well as an illuminated Check Engine Light.
Car Hesitates When Accelerating From Stop, Reasons #12: Catalytic Converter
Since 1970, catalytic converters have been a primary emission control system in many vehicles. It is located in the exhaust pipe and operates at extremely high temperatures. The reason behind the high temperature is the need to incinerate specific toxic exhaust gases before they are released into the atmosphere.
A good catalytic converter will last the total service life of the vehicle. However, that does not mean they are immune to failure. A poor catalytic converter results in a decrease in power, stuttering, and poor fuel economy.
Car Hesitates When Accelerating From Stop, Reasons #13: Spark Plugs
One of the fundamental components ensuring smooth engine operation is the spark plug. Responsible for igniting the fuel-air mixture in the combustion chamber, a worn-out spark plug can directly impact acceleration. Over time, these plugs degrade, leading to weak sparks, misfires, and inefficient combustion.
A failing spark plug may also cause poor fuel economy, rough idling, and increased emissions. Luckily, replacing spark plugs is typically straightforward and affordable. Regular maintenance schedules often include this task, ensuring engine performance remains consistent.
Car Hesitates When Accelerating From Stop, Reasons #14: Transmission Issues
While many acceleration issues stem from the engine, don’t overlook the transmission. It’s the bridge between the engine and the wheels. When transmission fluid becomes dirty or if there’s a malfunction within the system, this can result in hesitation when trying to accelerate.
Signs of transmission problems include rough or delayed shifts, grinding noises, or slipping gears. Regularly changing transmission fluid and having periodic inspections can prevent many potential issues in this area.
Car Hesitates When Accelerating From Stop, Reasons #15: Vacuum Leaks
The engine relies on a precise balance of air and fuel for optimal combustion. Vacuum hoses and connectors maintain negative pressure, aiding in various tasks, from fuel vapor delivery to air intake. A leak can interrupt this balance, causing your vehicle to stumble or hesitate when accelerating.
Symptoms include high engine idling, reduced fuel economy, and even a hissing sound under the hood. Detecting and fixing vacuum leaks can often restore your car’s acceleration to its normal state.
Car Hesitates When Accelerating From Stop, Reasons #16: Clogged or Failing PCV Valve
The Positive Crankcase Ventilation (PCV) valve plays a role in controlling the flow of crankcase fumes. A clogged or malfunctioning PCV can lead to increased engine pressure, resulting in oil leaks or poor engine performance.
If your car exhibits symptoms like oil leaks, sludge buildup, or a decrease in performance, it might be time to check the PCV valve. Typically, replacement is straightforward and doesn’t strain the wallet.
Car Hesitates When Accelerating From Stop, Reasons #17: Electronic Control Module (ECM) Issues
The Electronic Control Module (ECM) can be thought of as the car’s brain. It manages and coordinates various aspects of the vehicle, including ignition timing, fuel injection, and engine performance. However, like any computer, the ECM can face glitches, affecting its ability to make accurate decisions.
Issues with the ECM can lead to a range of symptoms, from poor acceleration to stalling. Resetting or replacing a malfunctioning ECM is a task typically best left to professionals, given its integral role in the car’s operations.
Car Hesitates When Accelerating From Stop, Reasons #18: Timing Belt or Chain Wear
The timing belt or chain ensures that the engine’s valves open and close at precise times. Over time, these components can wear out or become misaligned. If this happens, it disrupts the engine’s timing, causing poor performance and hesitation during acceleration.
Regular inspections and adhering to replacement schedules can prevent untimely wear or sudden failures. Always consider the manufacturer’s guidelines when dealing with these components.
Car Hesitates When Accelerating From Stop, Reasons #19: Damaged or Failing Ignition Coil
An ignition coil’s purpose is to convert the battery’s low voltage to the thousands of volts needed to create a spark in the spark plugs, igniting the fuel. A faulty coil can lead to weak or irregular sparks, disrupting the combustion process.
Symptoms include a rough idle, reduced power, increased fuel consumption, and hesitation during acceleration. Often, coils are easy to replace, bringing immediate improvements in performance.
Car Hesitates When Accelerating From Stop, Reasons #20: Bad Ground Connections
Modern vehicles rely heavily on electronics. Bad ground connections can cause erratic behavior in various systems. A weak or faulty ground connection might affect how sensors report data or how actuators respond, leading to acceleration issues.
Ensuring that ground connections remain clean and tight is crucial. Periodically inspecting these connections can preemptively address potential issues.
In conclusion, there’s a myriad of reasons why a car might hesitate when accelerating. Regular maintenance and inspections are crucial in ensuring each component functions optimally, offering a seamless driving experience. When in doubt, always consult with a trusted mechanic to diagnose and address any underlying issues.
How To Diagnose
A mechanic will start by plugging into the vehicle’s ECU by using a code scanner/reader to understand what the actual problem is. On top of reading trouble codes, they should also get readings of fuel/oxygen intake to ensure that those numbers are what they should be. After the mechanic derives all the information they need, they can start to repair any potential problems.
1. Bad Mass Airflow Sensor
If the mechanic thinks that the problem is a bad mass airflow sensor, they will first inspect the sensor for any external damage. They will also make sure that the sensor is properly wired with no damage to the wire harness. Afterward, they should remove the mass airflow sensor before changing it with a new one (if needed).
In case the problem is with the fuel pump, they will take the fuel tank out and inspect it. If the mechanic’s doubts are confirmed, the tank will have to be replaced.
Should the mechanic think there is something wrong with the throttle position sensor, they will test the component along with its wiring to make sure everything is functioning right. If there is indeed an issue with the throttle sensor, the mechanic will remove and replace it.
In between taking out the old sensor and changing it with a new one, they should give the throttle body a quick cleanse. After everything has been installed, the mechanic will ensure the new sensor is functioning properly and send the right information to the vehicle’s ECU.
2. Possible Issues With Fuel Injector
The problem can also be a failing or dirty fuel injector. If they suspect something like that, the mechanic will have a look at the injectors and try to detect any signs of leakage or damage. The mechanic can also take this chance to change the fuel filter – given it isn’t a part of the fuel pump. The injectors will then have to be replaced and tested before you get to drive your car again.
In all cases, the professional will start the vehicle to ensure the newly installed components are functioning correctly. If a warning light has gone off, the mechanic can clear the trouble code with a reader/scanner.
Hesitation At Low Speed
If your car stutters when accelerating at low speeds, the frustration can start getting to you from the second you climb inside the vehicle. Doing something as simple as pulling it out of the garage can seem like a task when the car is sputtering out of control. You will start questioning if driving the vehicle is even worth it.
More often than not, a car that stutters at low speeds is suffering from a case of poor spark plugs. A basic tune-up should fix the jerking from the root. However, there can also be an issue with the catalytic converter or the air intake system. There are a few of the common causes of a cat stuttering when accelerating at low speeds.
Hesitation At High Speed
Perhaps the sole good thing about a car that jerks when accelerating at low speeds is that you aren’t burdened with the thoughts of losing control over it. As you will not be moving very fast, to begin with, the problems shouldn’t be that severe. But what about a car that stutters when accelerating at high speeds? That is a genuine problem capable of causing major damage.
If you are experiencing this problem, we suggest getting it taken care of as soon as you can. You shouldn’t put yourself and others in danger by riding around in a vehicle like that. Mostly, when a car hesitates when accelerating at elevated speeds, it is due to a lack of oxygen in the combustion chamber. To fix that, you will have to get the blocked air intake cleaned or replace a bad mass airflow sensor.
Repair Costs
You should not drive around in a vehicle that jerks when you accelerate. The car has to be brought to the repair shop immediately to be inspected. Contact your mechanic about the issues and let them take a look at them. They can diagnose the issue and repair it for you.
The cost of fixing this problem will differ depending on the particular issue. Check out some of the costs associated with repairing a few parts that may be responsible for a jerking car:
- Replace spark plugs: $50 – $150
- Replace air intake system: $150 – $500
- Clean fuel injectors: $50 – $100
- Replace catalytic converter: $1,000 – $2,500
- Replace accelerator cable: $100 – $375
- Mass airflow sensor replacement: $275 – $400
Again, the total costs of fixing a car that jerks when moving from a stop can change depending on the make, model, and year of your car. Your auto repair shop can give you an estimate of what it may cost. Don’t forget to count the labor costs which can pile up faster than you think.
Facts about Acceleration Problems
- Throttle lag is a common cause of slow acceleration, caused by factors such as a clogged mass airflow sensor or engine calibration issues.
- The easiest solution to throttle lag is installing a throttle response controller.
- Slow acceleration can also be caused by fuel system issues, air intake blockages, ignition, or engine problems.
- Throttle lag is the time it takes for the engine to respond to pressing the accelerator.
- Throttle lag can be improved by using the right fuel, cleaning the air filter, and checking the wastegate for turbocharged engines.
- Acceleration lag or surge can be caused by a dirty or faulty mass airflow sensor or a vacuum leak.
- Throttle position sensor (TPS) issues can cause hesitation or stall, along with symptoms such as a “sticking” throttle or poor fuel economy.
- To fix acceleration problems, check and replace air filters, fuel injectors, and spark plugs as necessary.
- Weak fuel pumps can cause hesitation, stalling, and difficulty starting, which can be diagnosed by a mechanic.
- Delayed acceleration can be caused by a variety of factors, including engine problems, fuel line blockages, and clogged air filters, which should be diagnosed by a mechanic.
In Conclusion…
When you want to diagnose a stumble or hesitation, it is essential to work your way through the entire diagnostic procedure logically and carefully. No need to assume the worst, and do not jump to conclusions. Begin with the basics (i.e. the air filter) before continuing with the others.
To interpret any trouble codes being displayed by the vehicle, you have to first be able to read the symptoms and decide why the sensor is sending those signals. Occasionally, a problem will trigger a long string of trouble codes and all of them have to be analyzed. So, if your car hesitates when accelerating from a stop, we hope you’ve found the solutions now!
