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Home / Symptoms / Not Accelerating

Four common causes for the vehicle accelerating badly and their related parts.

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Is Your Car Unable to Accelerate?

Your car isn’t accelerating because it has a low fuel flow. A clogged air filter, faulty injectors, or a damaged fuel pump might be the culprits. Alternatively, it can be damage to spark plugs or the timing belt.

There are several reasons why your car won't accelerate properly, ranging from simple issues like low fuel levels to complex problems like a faulty transmission or fuel pump. Unfortunately, troubleshooting and fixing the issue alone can be risky if you lack the necessary expertise or equipment.

Watch out: If you're noticing a slow acceleration or complete difficulty in accelerating your car, take note of the issue. Car acceleration problems can be a safety hazard to you and other drivers.

The most common causes for the car not accelerating

The most common causes for a car not accelerating are:

Faulty fuel pump: The fuel pump controls fuel flow inside the vehicle, ensuring the combustion process in the engine receives the fuel amount needed to start the car and keep it driving. However, the fuel pump can fail, leading to combustion issues that impact the vehicle’s acceleration.
Clogged fuel filter: The fuel inside the vehicle always passes through the fuel filter so it can get clean and rid of debris. However, if the fuel filter is too old and dirty, it can get clogged. A clogged fuel filter causes problems and obstructions to the fuel flow, leading to combustion issues and acceleration problems.
Faulty spark plug seal: The spark plugs are an essential part of the engine that ignites the fuel, allowing the engine to run. If the spark plugs are worn out, they will not perform as well, causing fuel economy to decrease. Furthermore, when the seals between the metal and porcelain are blown, combustion gas can leak out, resulting in poor fuel economy.
Loose timing belt: The timing belt is a toothed belt that spins around some of the engine’s gears, causing mechanical movement that takes part in the combustion process. However, the gears might jump a tooth on the timing belt due to misplacement. This misalignment causes the check engine light to come on and the vehicle to lack power.
Clogged catalytic converter: The catalytic converter is an essential component in your vehicle’s emissions system; it’s a ‘box’ that receives all the gases the engine releases and processes them, filtering out their toxicity and releasing them as less dangerous to the environment. However, if the catalytic converter clogs up, the gases might build up inside in, causing the engine to become heavier with vapors, leading to acceleration issues.
Faulty injector: The fuel injector sprays fuel directly inside the engine during combustion, making the engine perform ideally and delivering its fuel demands. However, fuel injectors can fail or get clogged, resulting in bad fuel delivery and loss of engine performance.

Frequently Asked Questions

Is the RPM moving at idle?

A few sensors inside the engine perfectly time the injector, responsible for spraying fuel at the right moment, creating an explosion, and filling the car with power. It's controlled by the engine's computer, where the sensors are. If the computer fails, the injector won't spray fuel, causing the car to shake and have problems idling, such as RPM fluctuation.
Is the vehicle stumbling when hard accelerating?

The fuel pump chucks gas into your car's engine. It's powered by electricity and is located in the fuel tank. It ensures enough fuel gets to the engine for it to work correctly. But, if the fuel pump wears out, it won't be able to transfer fuel to the engine in the necessary amounts, like when you're accelerating. This lack of fuel makes the engine struggle and shake when you accelerate quickly.
Is the car cranking for a long time before starting?

The fuel filter is like a strainer for your car's gas. It catches any dirt or junk in the gas or from the fuel pump, preventing it from entering the fuel injectors and clogging them. But, if the fuel filter gets too dirty from wearing out, it can slow the gas flow to the injectors. This can make it harder for the car to start up quickly.
Is the vehicle most struggling to accelerate after being driven for a while?

The catalytic converter is like a cleaner for the dirty air from your car's engine. It needs a mix of fuel and air to work properly and stay clean. But, if your vehicle has a problem, like using too much or too little gas, or if oil or coolant is getting into the exhaust, the catalytic converter can get damaged and start to get blocked. When this happens, pressure builds up in the engine, making it harder for the car to speed up. You might notice this more the longer you've been driving the vehicle.
Is the "check engine" light on the dashboard?

The timing belt is like a conductor that helps the engine's parts work together in perfect harmony. It ensures that the crankshaft and the camshaft are in sync so that the valves open and close at the right time. But, if something goes wrong and the timing belt slips or is installed incorrectly, the engine's sensors will notice and turn on the check engine light to let you know something is wrong.
Has the vehicle's fuel economy dropped?

Spark plugs are essential components of the engine that help produce energy to move your car. They are like small screws tightly screwed into the engine's cylinders. When the engine turns on, the spark plugs help create a spark that ignites the fuel in the cylinders, generating power to move your car. Over time, the seals that keep the gases inside the cylinders can start to fail, and this can cause problems. When the seals are not working correctly, the gases escape, and the engine's efficiency will decrease. This decrease in efficiency can cause your car to use more fuel than it should, which means you'll have to pay more for gas.

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: Clogged fuel filter

The most common reason for a car not accelerating is due to a clogged fuel filter. The fuel filter helps to keep your vehicle’s fuel flow clean and debris-free for many miles. However, the fuel filter can only last so long, and after too long, the filter can get clogged up, resulting in obstructions to the fuel flow. A bad fuel flow results in acceleration problems and combustion issues.

Symptoms it causes: Apart from the car having acceleration issues you might notice engine misfires, bad fuel economy, combustion problems, etc.
Medium risk of priority: If the fuel flow is bad, your vehicle starts developing combustion issues resulting in bad fuel economy, bad acceleration, and low engine performance. Unfortunately, this type of problem can develop into engine misfires and bigger damages, leading to engine stalling in some cases.

How exactly does the fuel filter clog up?

The fuel filter, as with any filter, gets debris from the fuel and accumulates it, removing dirty particles. However, the filter can clog up after a long time of accumulating debris. It’s advisable to exchange the fuel filter every 20,000 to 40,000 miles. When the filter clogs up so much, it’ll act as an obstacle, obstructing fuel flow.

Go safe: Ask for a mechanic to inspect your vehicle’s fuel and combustion system to investigate if the fuel filter is clogging up 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 filter to fail. 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 clogged fuel filter

A fuel system inspection is the most transparent process to understand why your vehicle’s fuel filter is faulty. This is because many components surrounding the fuel filter and its wirings 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 clogged fuel filter.

A customer dropped off their vehicle and reported it was cranking for a long time before starting. This meant that if they left the car unused for 15 to half an hour, the engine would take about a minute of cranking before it started. However, if they tried to restart the vehicle immediately after turning it off, the engine would start right up.

During the test drive, the technician confirmed that the engine took a while to start. However, the technician didn't notice anything unusual during the vehicle health inspection. Therefore, the customer authorized additional diagnostic costs to get to the root of the problem.

The technician used a specialized scanner to check for trouble codes but found none. They then checked the fuel pressure at the fuel rail, finding that it took extra time to build up to the manufacturer's specified pressure. The technician also noticed an inline fuel filter that didn't look like it had ever been replaced.

Next, the technician hooked up a pressure gauge to the pressure side of the filter and found that the pressure immediately came to the manufacturer's specifications. However, the pressure on the outlet side of the filter took a while to build up, indicating that the fuel filter had a restriction.

This restriction was causing the long cranks the customer reported. The technician determined that the fuel filter would need to be replaced to solve the issue.

Clogged fuel filter

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

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 Unable to Accelerate?

The most common causes for the car not accelerating

Frequently Asked Questions

Is the RPM moving at idle?

Is the vehicle stumbling when hard accelerating?

Is the car cranking for a long time before starting?

Is the vehicle most struggling to accelerate after being driven for a while?

Is the "check engine" light on the dashboard?

Has the vehicle's fuel economy dropped?

Typical fixes to address the cause(s)

The most common cause: Clogged fuel filter

How exactly does the fuel filter clog up?

Transparency example in a clogged fuel filter

Similar Symptoms

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