The reasons your cargo van won’t go over 20mph are:
- Failed catalytic converter
- Dirty mass air flow (MAF) sensor
- Dirty or clogged fuel filter
- Oxygen sensor
- Throttle position sensor
- Camshaft position sensor
- Bad ignition module
- Transmission control module (TCM)
- Clogged air filter
- Fuel pressure regulator
- Low transmission line pressure
However, keep in mind that it’s quite difficult to pinpoint the exact issue without having the codes read first.
You can visit a local auto parts store and have someone who knows what they’re doing read your cargo van’s computer for any fault codes.
The 5 Most Common Reasons
Although there are a dozen of potential causes, here are the 5 most common reasons your cargo van won’t go beyond 20 mph. I will put the less common reasons after them.
1. Failed Catalytic Converter
It’s safe to say that catalytic converters are an integral part of modern vehicles and any issues with this component of the exhaust system can lead to reduced power and acceleration.
These metal canisters are installed in the exhaust system of cars, trucks, vans, etc. with the sole intention of decreasing pollution by converting harmful emissions into non-harmful gasses via a chemical reaction.
In fact, a catalytic converter is meant to be rather durable and should typically last for up to 10 years (or more), although this doesn’t make it failure-proof.
Some typical symptoms of a failed catalytic converter:
- Decreased engine power and performance
- Exhaust smells like sulfur
- Rattling noises coming from underneath the vehicle
- The Check Engine Light appears on the dashboard
- Failure to pass the emissions test
A clogged converter will restrict exhaust flow, while a cracked one will leak harmful gas.
Keep in mind that the particular symptoms depend on the type of failure your catalytic converter is experiencing.
More specifically, if your converter is cracked it will start leaking harmful gasses into the atmosphere, while a clogged one will limit the engine’s exhaust flow.
2. Defective Mass Air Flow Sensor
The mass airflow sensor (or MAS for short) is an airflow sensor that is connected to the inlet air cleaner, and it essentially measures how much air is being fed to your engine.
The air mass that is detected and measured by this sensor is crucial for the ECU (engine control unit i.e. the brain of your van) of your van as the ECU decides how much fuel the engine needs based on this information.
So if your MAS is faulty and gives false readings, your engine’s ECU won’t be able to deliver the right amount of fuel at the right time.
And as you can imagine, this can lead to your vehicle consuming too much or too little fuel, which can result in really poor performance.
Common warning signs of a faulty MAS include:
- Difficulty accelerating
- Rough engine idle
- Bad fuel economy
- Black smoke from the exhaust
- Surging or hesitation during cruising or acceleration
- Trouble starting the engine (or the engine stalls shortly after being started)
- Check Engine Light is on
Regardless of the symptoms, a faulty MAS will most likely bring a particular code that’ll be stored in the vehicle’s computer.
In this case, a mechanic who has an ECU diagnostic tool will be able to read and interpret any related fault codes.
3. Bad Fuel Filter
Every vehicle that’s powered by an internal combustion engine (gasoline or diesel) is equipped with a fuel filter.
This filter is meant to remove any dirt or debris that can be found in the oil before it reaches the engine.
As a result, after a while, the fuel filter might become too dirty or even clogged, which can negatively impact your cargo van’s ability to reach and maintain higher speeds.
The standard symptoms of a clogged fuel filter are:
- Engine misfire and reduced performance
- Having a hard time accelerating
- Engine stalls while driving
- Difficulty starting
- Random engine misfire
Don’t forget that fuel filters aren’t permanent and they have to be replaced after a while.
It’s typically advised to replace your fuel filter once every 2 years or once every 24,000 miles – whichever comes first.
But the specific miles covered between replacements will largely depend on your engine, the fuel that you use, and your driving habits (e.g. more city or freeway driving).
4. Throttle Position Sensor Malfunction
The TPS is a vital part of your cargo van’s fuel management system as it detects what the throttle valve opening angle is, based on data provided by the accelerator pedal.
All of this data is processed by the TPS that then transfers this information to the vehicle’s brain (the ECU.)That’s how your cargo van determines how much fuel to dump into the engine.
Or in other words, if your throttle position sensor functions correctly, your vehicle will have adequate fuel economy, while also running smoothly regardless of whether you’re coasting, accelerating or cruising.
But this sensor sometimes tends to malfunction, which affects one of your engine’s most important systems – the fuel management one.
How to spot a faulty throttle position sensor:
- The vehicle accelerates but won’t shift up or go past 20-30 mph
- Lack of acceleration and power or sudden acceleration (the vehicle accelerates on its own)
- Rough idle
- The engine misfires or stops completely (it stalls)
- Noticeably decreased gas milage
- Changing gears becomes difficult
- The Check Engine Light flashes
Having a properly working TPS is vital if you want to get the most out of your cargo van’s fuel efficiency and performance.
Note that any potential failure of the throttle position sensor can have a very detrimental effect on your vehicle, your driving experience, and even your road safety.
5. Clogged or Dirty Air Filter
If the engine control unit (ECU) is the brain of your van and the engine is its heart, then the air intake through the air filter can be considered its lungs.
Gasoline and diesel engines require air (oxygen) for combustion to take place.
This makes the air filter a fundamental component of any internal combustion engine as it has to supply the engine with cleaner air that’s required for optimal performance.
A dirty or clogged air filter can literally suffocate your engine, but the good news is that identifying a bad air filter is quite easy.
The most typical symptoms of a dirty air filter are:
- Sluggish acceleration and reduced power
- The air filter looks dirty (brown or black in appearance)
- Engine hesitates upon start or rough idle
- Vibrations, hiccups or rattle on idle
- Fuel economy worsens
- Black smoke or even fire coming out of the exhaust system
It’s generally advised to replace your vehicle’s air filter once a year or between 12,000-15,000 miles – whichever comes first.
However, the precise frequency of air filter change for your cargo van also depends on where you live.
For example, if you live in a clean rural area, you shouldn’t need to change your vehicle’s air filter as much as someone who lives in a big city.
Four Quick & Easy Fixes That You Can Try Right Now
Before heading over to a qualified mechanic to inspect your van, give these simple and easy fixes a try:
1. Check the Fuel
The first step is to check your fuel level, as the issue might be caused by driving with little to no fuel in your cargo van’s fuel tank.
Apart from that, make sure that your van is filled with the right type of fuel, because if you’re using low-quality fuel that is contaminated with debris or dirt, the fuel lines and filter might get clogged.
If you’re unsure that you’ve used the right octane number for your vehicle, try to refill with the proper fuel type and see if that makes a difference.
2. Check the Parking Brake
Since cargo vans don’t typically have the same level of fancy electronic assistants as cars, they most often have regular (non-electric) parking brakes (a.k.a. handbrake or emergency brake).
When the parking brake is engaged your rear wheels become fully or partially locked (depending on whether your handbrake is fully engaged or not), which results in a significant drag of those wheels.
And if you forget to disengage your parking brake before pulling away, your vehicle will experience a noticeable loss in power and acceleration.
So make it a habit to always check your parking brake’s position before driving, especially when your van becomes sluggish and won’t go beyond a particular speed.
3. Check the Gas Pedal
Park your vehicle somewhere safe and see if you can find anything under or around the gas pedal that can potentially obstruct its free movement.
You might be shocked to find that there’s been something stuck under your van’s gas pedal, which wouldn’t let you push the pedal all the way, hence why it won’t go over 20 mph.
Of course, it most likely won’t be something that makes noise when pressed (e.g. a plastic water bottle) so make sure to inspect the area below and around the gas pedal carefully.
4. Consider the Altitude that You’re Driving at
If your cargo van doesn’t want to go above a specific speed and if you drive in a high altitude region, then your engine could suffer from the lower air density in these areas.
The higher you go the lower the air density will be which there’s less oxygen in the air.
This can decrease your vehicle’s power, which can become even more noticeable if your van’s air filter is clogged.
If Nothing Helps – Visit a Skilled Mechanic
Eventually, if the problem persists, your only logical option would be to take your car to an auto repair shop and tell them about your woes.
A qualified mechanic with the proper equipment and computer diagnostic tools should be able to pinpoint the exact problem that causes your van to not accelerate beyond 20 mph.
It’s worth mentioning that your repair bill might not be that high if the issue turns out to be something simple such as a clogged fuel or air filter.
But even if you have to pay more than expected, it’s definitely worth paying as much as needed to fix this issue.
Remember that your vehicle’s ability to properly speed up (within state limits) and maintain higher speeds (e.g. on a freeway) is important for your safety and that of other drivers.
Eventually, your cargo van may not be able to go above 20 mph due to various possible malfunctions and failures.
But they can be summed up under 2 main categories:
- Mechanical problems – Bad catalytic converter, clogged fuel filter, malfunctioning injectors, dirty air filter, low compression, faulty fuel pump
- Sensor/ECU issues – Malfunctioning MAF sensor, bad fuel pressure regulator, defective oxygen sensor, camshaft position sensor
And while the root cause of your problem could be something as simple as a stuck object under or behind your gas pedal, your best bet would always be to take your van to a qualified mechanic.
Now, how long have you been dealing with this annoying issue?