Car Won’t Accelerate At High Speeds? (Easy Checklist)

Problems with acceleration can often prove tricky, with most drivers only noticing such an issue when trying to accelerate in high traffic.

This could mean a host of things, some being easy fixes while others require an expert’s services for repair.

If you have encountered such a problem, the following guide will be your go-to in troubleshooting some common acceleration issues.

We’ve previously looked at why a car might not accelerate past 60 MPH and now it’s time to look into acceleration problems at high speed.

Check this article specifically if your diesel vehicle won’t accelerate.

Ford Fusion dashboard

Common Issues That Call for a Quick Fix

Not all problems will need a technician to solve, with a simple check being enough.

Examples of some common issues that require a quick fix are:

Your Emergency Brake Is Engaged

If your emergency brake is engaged, whether partly or fully, you will likely have issues during acceleration.

If this is the case, your brake may be pressing the brake pads on your tires, interfering with your acceleration.

Disengage the emergency brake to rectify this.

While this will be an easy fix, make it a point to follow up with your mechanic. Friction and overheating could cause your rear brake pads and wheel drums to warp and may need more attention.

Altitude Interference

Higher altitudes could be another reason you have trouble accelerating during uphill drives or on sharp inclines.

Reduced oxygen has been found to cause a 20% reduction in power, hence the slow speed.

To avoid future problems, make it a point to clean your fuel injectors and air filters, as this helps reduce tension when driving uphill.

Fuel Trouble

Fuel issues will likely be the most common issue when your car does not accelerate at high speeds.

The first indicator of this will be a low fuel tank. Fuel powers your vehicle, meaning a low tank will not offer enough acceleration energy.

Getting the wrong type of gas for your car could be another problem, with gas containing debris also clogging your filters and gas lines.

To rectify this, refill your tank with the right fuel.

You can also experience trouble accelerating before the vehicle has warmed up.

Stuck Objects Under the Gas Pedal

You may occasionally drop items under your feet when driving or parking and forget to collect them.

If these get into the space under your gas pedal, they will likely interfere with your control and acceleration.

To prevent such mishaps, collect any items you drop onto your car’s floor immediately after they fall.

Your Vehicle Needs a Thorough Clean Up

Dirt is one of the leading causes of damage to internal engine parts, with debris often causing poor engine performance, excessive oil consumption and total engine failure.

With this in mind, cleaning your vehicle will be a crucial part of your maintenance, with failure to do this resulting in the following problems.

Debris in the Mass Air Flow Sensor

If your car won’t accelerate past 4000 RPM, it might also be due to problems with the air flow sensor.

The oxygen sensor or mass airflow (MAF) sensor is responsible for measuring how much air flows into your engine. If it is dirty or has debris, it could send the wrong readings to your engine.

When this happens, your engine may use too much fuel or too little, causing problems when you need to accelerate.

Like other components of your vehicle, ensure that your MAF sensor is clean to prevent this.

Dirty Air Filters

Clean air flow is a critical part of your vehicle’s internal systems, with any disruption limiting fuel combustion and airflow to the rest of the system.

Check for debris and clogged parts in your air filters, with too much dirt requiring a change of your filters.

Vehicles will often come with instructions on how often the air filters should be replaced, allowing you to get the most out of your car.

Dirty Spark Plugs

If your spark plugs are dirty, misfiring issues could result in poor acceleration at high speeds.

Your spark plugs must be clean at all times to enable them to hit the cylinder at the right time, eliminating any misfiring mishaps.

The ignition should also be free of debris as this often works hand in hand with the spark plugs.

Dirty Fuel Injectors

Another reason that could be affecting your acceleration is a dirty fuel injector.

When clogged, fuel injectors result in poor fuel flow, causing severe acceleration issues. Consider getting a fuel injector cleaning additive for your gas tank to fix this.

Clogged Fuel Filters

Clogged fuel filters will also be a problem when accelerating at high speeds.

Fuel filters protect the engine from sludge and debris that could clog your gas tank. Clogged fuel filters make it impossible to dispense fuel throughout your car, limiting the power when driving at high speeds.

Replace any clogged fuel filters and have these checked during your vehicle servicing.

Technical Issues That Require the Help of a Professional

While taking care of the above will require simple solutions, technical problems will need an expert’s help.

As vehicles age, parts such as the clutch and fuel pump get worn out and need to be replaced. Maintaining such parts will be important in getting safe driving on the road, minimizing fatalities that often crop up due to technical failures.

With this in mind, take note of the following:

TPS Monitor Malfunctions

The TPS refers to the throttle position sensor.

This is responsible for monitoring the angle of the throttle controlled by the accelerator pedal, after which it sends information to the ECU.

If it malfunctions, it will send the wrong information, causing a setback to how the system should adjust. This could translate to erroneous acceleration when driving at high speeds.

Damaged Timing Belt

As previously stated, every component is essential in how well your vehicle adjusts to information flow, with the timing belt not left behind.

A damaged timing belt will, therefore, not be sufficient to keep the internal combustion engines running, making it a problem when you need to drive faster.

A few issues causing this could be wear and tear that can be fixed by a quick replacement or poor installation that requires adjusting the belt.

A damaged timing belt may also cause the car to not downshift during acceleration.

Engaged Limp Mode

If you are trying to accelerate at speeds over 25 mph and your vehicle fails to respond, your vehicle likely has its limp mode engaged.

This safety feature kicks in to preserve your engine and prevent it from getting damaged, allowing you to drive safely to your destination.

A few factors that could result in an engaged limp mode include:

  • Faulty engine sensors
  • Clutch malfunctions
  • Gearbox malfunctions
  • Problems with the brake system wiring
  • Brake problems
  • Low transmission fluids

Problems With the Electronic Control Unit

The electronic control unit (ECU) is responsible for controlling the electronic features in your car, from fuel injection to traction control and transmission.

It evaluates these parameters and sends information to the sensors, allowing your vehicle to affect the fuel and energy levels based n your driving needs.

If the ECU is faulty, it will likely cause setbacks in multiple areas of your vehicle.

This could be transmitting erroneous air flow readings and causing faulty timing of the spark needed for ignition. Additionally, your vehicle may also be experiencing circuit problems such as loose connections and damaged wires.

Data network problems could also interfere with your ECU, resulting in faulty readings causing poor acceleration.

Rectifying this will often need professional help, with mechanics trained to repair and reprogram it.

This could also cause your car to not accelerate when turning.

A Faulty Clutch

The clutch helps engage and disengage power transmission between the driving shafts and connects the rotating shafts beneath your hood.

A faulty clutch will not engage the transmission fluid as it should with the engine, causing problems with your acceleration.

In other instances, it could also result in speed changes when you are unaware, causing a deceleration or acceleration that puts you in harm’s way. This will often be linked to low transmission fluid levels, requiring urgent servicing.

Compression Issues

The compression allows the engine’s pistons and valve to transport fuel and air to the areas of your vehicle that are needed, making it possible for your car to move and function.

Without this, you may experience misfiring, often visible when you experience a decrease in the power output when you need to accelerate.

Fixing the compression could mean replacing the broken parts of your compression system, whether the piston, camshaft or piston ring.

In addition to this, your technician may need to check for issues such as a faulty head gasket and worn-out cylinder walls.

Damaged Catalytic Converter

The catalytic converter is critical in converting toxins from the car engine emissions to safe by-products such as water vapor and carbon dioxide, allowing your vehicle to reduce harmful emissions.

If damaged, the catalytic converter can cause the engine to stall due to increased exhaust pressure.

A few signs to watch out for include:

  • Dark exhaust smoke
  • sluggish engine performance
  • The smell of rotten eggs or sulfur
  • Reduced acceleration
  • Excess heat under the vehicle

Turning the engine off can be a simple remedy to avoid ruining the converter further until help gets to you.

Problems With Other Engine Management Systems

Not all issues will be easy to diagnose, with most management issues being challenging to spot.

Examples of faulty engine management systems include:

  • Problems with components related to the turbocharger
  • A faulty cylinder deactivation system


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