Have you ever wondered about problems like the car won’t go over 40? Well, it is such a common issue for numerous vehicles.
When pushing on the gas pedal, you often expect the car to go faster based on the pressure added to the engine.
But sometimes, the vehicle tends to hesitate, or the acceleration is quite slow. In the worst conditions, it could become a road hazard.
It would be better to determine why the car won’t go over 40 mph for better safety with the ride. And then, you can find practical solutions.
Car Won’t Go Over 40 – What’re Causes?
When your car won’t go over 40 miles per hour, several dirty parts, technical failure, or even your mis-concentration, etc., all could be possible causes preventing the car from accelerating.
In particular, the symptoms commonly occur on vehicles with high mileage.
In the beginning, drivers tend not to notice the signs. However, the situation changes when they drive up a hill or accelerate on the road.
For months, the problems could become much more severe to damage your vehicle engine.
Now, let’s dig deeper into the reasons why the car won’t go over 40 after inspection.
1. Simple Issues
Sometimes, my car won’t go over 40 mph could come as a result of several simple issues.
If you are in the same situation as me, you can detect and solve the problems yourself without visiting the mechanic.
Altitude
The low air density often comes with the high altitude. This condition is likely to cause the car to run on a sharp incline.
The lower the level of air components such as nitrogen and oxygen, the less power the vehicle has (commonly 20% reduction).
Parts Under The Gas Pedal
Regardless of technical problems, something (balls, papers, etc.) that drops under the pedal can affect the acceleration.
Taking a look at those things even for seconds could limit your concentration to accelerate or decelerate the vehicle.
Emergency Brake
The partly or fully engaging emergency brake can press the pads featured on the rear tires. The problem causes the brake to move and affects the acceleration.
By disengaging the brake, you can fix this issue. But it would be better to have a check with an experienced mechanic.
Fuel
What will happen with the car if its fuel tank nearly runs empty? It could be the answer to the issue when my car won’t go over 40 miles per hour.
The engine finds it hard to get enough acceleration energy with a nearly empty fuel tank. At the same time, the bad fuel with the debris and dirt buildup can clog up the filters and lines.
You should refill that tank with the right amount of fuel needed.
2. Dirty Parts
Inside the engine, numerous parts interconnect to keep the car running smoothly. Only one gets any buildup of debris or dirt that could damage the whole engine.
Unless you know about proper cleaning and replacing methods, the best solution is to ask an experienced mechanic for help.
Dirty Spark Plugs
Both ignition coil and spark plug can be a cause of misfiring. Unless the spark plug can get the cylinder at the right time, these parts will do nothing for the engine.
The lack of misfires sometimes is the main reason for the acceleration issue. So check for a dirty, clogged, or oil-fouled spark plug.
Malfunction In Oxygen Sensor
The oxygen sensor is a part which monitors the amount of exhaust emission of the engine. In other words, its function is to analyze the vehicle’s fuel-air ratio through the whole engine.
If this sensor goes wrong, the car computer unit will not receive the data related to the fuel and air. Then, it causes an unreliable accelerating performance even when you press the pedal.
Clogged Dirty Fuel Filter
The fuel filter does its function of protecting the engine from debris, dirt, and sludge. The dirt buildup could degrade the gas tank if the filter gets clogged.
Consequently, the flow of clean fuel cannot reach through the engine. Hence, it prevents the acceleration from performing well.
Dirty Clogged Air Filters
Like the fuel filter brings clean fuel for the engine, the air filter provides clean air. The line sends a mixture of air and fuel to combustion chambers for the burning process.
If the filter gets clogged, there will be no right mixture to run. For days, this failure results in an improper acceleration.
3. Technical Problems
For a smooth driving experience, it must be a combination of moving to work together simultaneously. However, those parts tend to wear out over time due to age or misuse.
And all of them could break out the accelerating performance.
For example, a full fuel tank helps keep the fuel pump cool. In other words, frequent running based on the nearly empty fuel tank can cause the fuel pump to wear out in a very short time.
And the following is a list of several technical problems affecting your car’s acceleration. Most of them often require professional mechanics to check and find solutions.
Limp Mode
When the car won’t go over 40 rpms jumping up and down, it could stay in limp or limp home mode. Drivers often call it the feature of preservation.
In other words, that mode gets the vehicle home with an auto mechanic without any damage. For easy problem-detecting, it comes with the check engine light.
Thus, if you find strange signs with the light, I recommend checking your vehicle with a mechanic.
Failed Clutch
In another case, the problem related to acceleration could link to the clutch. Assuming that the clutch fails to engage the transmission fluid inside the engine.
Then, a lower level of transmission fluid will come to prevent the engine from decelerating or accelerating.
Malfunctioned TPS
TPS stands for the throttle position sensor. It plays an important role in detecting the opening and closing angle of the throttle valve controlled by the accelerating pedal.
After detection, TPS will send the data to ECU (electronic control unit).
The TPS malfunction occurs when TPS loses its ability to read the throttle’s position accurately. As a result, it could send wrong information to ECU to control the vehicle.
Timing Belt
The timing belt always stands on the top list like a VIP when it comes to the car engine components.
The belt’s stopping mode (even one tooth only) is enough to cause a considerable problem for the vehicle’s acceleration. It is because of both improper and misaligned installation.
Catalytic Converter
Another culprit for the car won’t go over 40 and shakes is the catalytic converter. Any fault in this part can produce the backpressure added onto the whole engine.
Due to the additional pressure, the vehicle gets trouble with acceleration.
In a worse situation, it could catch fire – a terrible unexpected accident.
Thus, it would be better to pull over and then turn off the engine if you smell some sulfur or rotten-egg smell. And do not re-start the car till you have the problem fixed by a mechanic.
Compression Issues
Both fuel and air van go through the engine to different corners when needed, thanks to the vacuum line.
But the engine cannot operate properly with a broken line. Hence, if the car cannot accelerate, it is time to check this part.
Does Your Car Need A Mechanical Care?
The answer should be a big YES in some cases.
A Dangerous Slow Driving
It is unnecessarily an issue if you drive the vehicle at a reasonably slow speed. For cases like the traffic at rush hour, it would be better to decelerate the car. That said, you should not take this problem lightly.
Slow driving, sometimes, is not as safe as speeding, for sure. A driver decelerating the car will force others to adapt at the same speed.
The sudden simultaneous deceleration can lead to an increase in the risk of accidents. And it will become more dangerous to change lanes.
In numerous states, it constitutes a traffic-related non-crime violation. Hence, policies can fine you with a traffic ticket. In California, for example, speeding tickets cause the insurance premium to go up.
An Urgent Mechanical Check When Car Cannot Accelerate
Not all drivers prepare the necessary knowledge and skills to detect and fix vehicle issues. If it is also your case, it will be better to meet an expert.
I suggest registering for a roadside or travel assistance member card for a discount. In general, that service is available in most areas.
It is never a good idea to drive a car with issues related to acceleration/deceleration. Mechanical failure leads to accidents and degrades your vehicles over the years.
Hence, my high recommendation is to learn to know more about your cars to care for them properly.
Conclusion
So now, when the car won’t go over 40. It is no longer a big problem at all. When you know what it is, you can find the best solutions right away.
Hopefully, our explanation will be helpful for your journey with the lovely vehicle.
For more support, feel free to drop me a line.