7 Causes of a Delayed Response When Pressing the Accelerator!

Driving is like a conversation between you and your car. You press the accelerator; it responds with the requested speed. However, imagine if there’s a sudden silence in this two-way chat. This can lead to bumps in your otherwise smooth ride. So, why is there a delayed accelerator response?

Throttle body issues are the primary culprit behind throttle lag. Whether it’s the consequence of accumulated grime or a malfunctioning position sensor, the vehicle’s response to the accelerator pedal input gets delayed. Besides that, fuel or air delivery system problems can also trigger acceleration delays.

Before you read on, there are different ways to describe a delay in throttle response and different times to experience it. So please bare that in mind. Usually, things like engine hesitation when accelerating can be caused by the same or other issues, even though they are similar faults. Pressing the accelerator pedal doesn’t necessarily mean you are driving. For example the throttle delay only be when at idle.

How does An Accelerator Function? 

The accelerator (gas pedal) is your car’s speed controller. When you press the accelerator pedal, you tell the car how fast you want to go. The harder you press the pedal, the more fuel and air you’re requesting the engine burns in the combustion process to keep up.

As you press the pedal, you open a door (throttle body) that lets more air into the engine. Think of it like opening a window to allow more air into a room. However, instead, the engine control unit delivers the message from the accelerator to the throttle body.

When the pedal is pressed, the ECU opens the throttle based on how hard you press the pedal. Then, a throttle positioning sensor (TPS) reads the position of the throttle and sends it back to ECU. Based on this information, the ECU calculates the fuel quantity that is to be injected into the engine. Regardless of whether your engine uses diesel or petrol, what happens after you press the throttle pedal is the same. 

7 Causes of a Delayed Response When You Press the Accelerator Pedal

There are instances when you observe a lag or delay in the acceleration. This lag can be frustrating, especially if you’re cruising on a highway and your car responds poorly.

Here’s a list of possible reasons why the car behaves oddly:

1. Problems within the throttle body

The throttle body controls the amount of air that goes into your engine. If the throttle body gets clogged with dirt or grime, the throttle plate can’t open or close as it should, leading to acceleration problems such as delayed response, sticking gas pedal, and jerking when accelerating. 

Also, in newer vehicles, the throttle body uses a motorized actuator controlled by the car’s ECU to regulate the throttle opening. If this actuator starts acting oddly or goes wrong, it could result in the same issues. 

The usual cause of a dirty throttle body is failing to change the air filter regularly.

2. Tps sensor malfunction

The Throttle Position Sensor (TPS) tells your ECU how open the throttle plate is on the throttle body, basically how far down you’re pressing on the gas pedal. If the TPS fails, the ECU won’t get the correct information. Without the ECU knowing the correct throttle position, that car won’t inject the required amount of fuel, which will cause a delay or jerking when accelerating.

3. Cvt transmission

Sometimes transmission can be a source of lag, especially if you have continuously variable transmission (CVT).

CVT works differently from traditional automatic or manual transmissions. It uses a rubber belt and two pulleys that can change sizes, which allows the engine to operate at the most efficient speed.

However, the common issue with CVT is the ‘rubber-band’ effect, which is a delay in the transmission response as the power is slowly transferred to the wheel. The rubber band effect effectively does the same as driving with a slipping clutch. However, no damage is being done, as this is the transmission’s way of protecting itself from abuse when accelerating hard. 

4. Dirty air filter

Air is equally essential as fuel for the car. The air passes through a filter to ensure the engine receives clean air. However, if the air filter is too dirty or clogged, it can’t let in enough air. Just as you have difficulty breathing with a stuffy nose, the engine behaves similarly. 

The most common cause of a clogged or filthy air filter is neglecting to change it regularly. Although with a severely clogged air filter, the engine would shut off. Occasionally, you can get a delay in throttle response while the engine waits for the air to pass through the filter. However, the car will run extremely rough until you change the air filter. 

5. Fuel delivery issues

Just like issues with the air being delivered into the engine, causing a delayed pedal response. Without the necessary fuel required precisely when the engine needs it, throttle response could be delayed.

Depending on the severity of the issue, you may experience a slight delay before the engine receives the total fuel load it requires. The usual fuel delivery issues are:

Poor quality fuel or debris in the bottom of the gas tank can usually be blamed for these problems.

6. ECU issues

The Engine Control Unit (ECU) is like the brain of your car. It controls many parts of your vehicle, including the throttle body, the TPS, and the fuel system. If there’s a glitch or error in the ECU, it can cause a delay in acceleration.

It could be due to a software update required, or the ECU might need a reset, i.e., the engine management light is on. This usually happens if you’ve recently installed new sensors, and the engine will only run right once they are recalibrated. 

7. Weak spark

If the engine receives the correct fuel-air mixture, it needs a strong spark delivered on time to burn it and complete the combustion process.

There are two usual areas for concern. One is the coil pack which converts low battery voltage into the high voltage needed to power the spark plugs. Coil packs typically break down with age, but it’s extremely common to find failing coil packs in certain cars.

The other issue is eroded spark plug tips, which are worn out and no longer provide a strong spark. Both problems can cause delays in throttle response and jerking when driving at a constant speed, especially in the early stages of failing.

How to Get Rid of Delayed Response When Pressing Accelerator?

If you’re experiencing an accelerator pedal lag, there are a few steps you can take to resolve it the issue. Before you do, you should know that wear and tear will set in on older vehicles, and minor delays in gas pedal response may be present on well-used, worn engines. No matter how much time and effort you put into repairing this problem, you may never cure it.

Clean the throttle body

Over time, the throttle body can accumulate grime and dirt, slowing its response. Cleaning the throttle body can help improve this. It usually involves removing the throttle body from the engine, but sometimes you can still do it in situ. Carefully clean it with a carb cleaner and a toothbrush, paying particular attention to cleaning any grime from the throttle plate and any springs that may be visible. 

cleaning throttle boy to fix throttle delay

Check for diagnostic trouble codes

Connecting the car to an OBD-II scanner to check for any diagnostic stored fault codes. Just because the engine management light isn’t on doesn’t necessarily mean the vehicle isn’t suffering from a faulty sensor. 

Check the serviceable items. 

Check the condition of the serviceable items, such as the spark plugs, fuel filter, and air filter. If you last replaced these items a long time ago, it’s good maintenance to replace them, and it doesn’t cost the earth. Even if they don’t cure the delayed response when pressing the gas pedal, the engine will run smoother. 

Final Thoughts

With a minor delay response when pressing the accelerator pedal, it can be troubling, especially if you need to accelerate hard and get yourself out of a situation. For these reasons, you should look at repairing this issue asap. Cleaning the throttle body and changing the air filter will likely cure this issue. But if not, diagnosing the fault can be tricky, so I suggest having a mechanic take a look for you.

My name is Tom although my friends call me Tommy. Messing around with cars and bikes has always been a hobby of mine even from a young age. So I made it my day job 17 years ago. I am a fully qualified mechanic as you would expect. I've worked in all different areas of the motor trade, valeting, panel beating, engine repairs, I'm sure you get the idea. I enjoy sharing my wealth of knowledge and experience with others, which is the reason I spend a lot of time here writing for this website.

4 thoughts on “7 Causes of a Delayed Response When Pressing the Accelerator!”

  1. Hi Tommy,
    Hope its ok to ask you a question regarding my mums car.
    When the engine is first started and I then press the throttle peddle there is no rev’s, nothing at all. Could this still be the TPS or the throttle control body? as it happens in neutral.
    Best wishes for the New Year.
    Kind regards,

    • Hi Karl,
      Happy New Year to you as well! Thanks for your question.
      Without more information on the make, model, and year of the car, etc., it’s difficult to say for sure; however, I would certainly start by looking at either the throttle position sensor(TPS) or if the throttle body has an electronic throttle control system (ETC). The only way you will determine which component is faulty is by plugging it into a diagnostic machine. If you are saying it is only happening in neutral, I would presume it is an electrical fault.
      Good luck, and let me know how you get on.

  2. my 05 250ford truck is having problem starting up and running, when step on the accelerator nothing happens … the engine dose idol very roughly

    • Thanks for your comment. If the very rough idle and the check engine light are on, the car could be in limp mode, which would explain it. If it’s not limp mode, from the limited information, I would start by looking at a fuel supply or ignition issue. Regardless, it would be impossible to say exactly what has caused this without plugging the car into a diagnostic machine to see what’s happening.



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