Are you experiencing that annoying problem when your car shuts off while driving out of nowhere? Don’t worry, we’ll help you!
In modern vehicles, there are many sensors and functions to keep your car running smoothly. Having a basic knowledge of your vehicle can help you counteract a mechanical problem, such as your car turning off while driving.
In this article, we will look at the most common reasons and show you how a professional mechanic would fix them. Let’s go.
7 Reasons Why A Car Shuts Off While Driving
#1. Faulty Crankshaft Position Sensor.
One of the most common reasons a car turns off while driving is a faulty crankshaft position sensor. The crankshaft position sensor’s role is to monitor the engine’s many moving parts, including the crankshaft, engine valves, and pistons.
It tracks the crankshaft’s velocity and location to help facilitate the optimal timing for fuel injection and ignition.
A failing crankshaft position sensor cannot provide the correct information about piston positioning in the engine to the Engine Control Unit, causing a cylinder to misfire.
If the crankshaft position sensor isn’t working properly, it can also cause the check engine light to come on. Another sign of the faulty crankshaft position sensor is that the tachometer isn’t working properly.
The tachometer is the gauge typically located next to your speedometer on your dashboard that reads the RPM’s in your car.
It typically increases every time you rev your engine. When the intended speed is achieved, the tachometer will stay put in its place.
If the crankshaft position sensor is faulty, it will send incorrect and abnormal data to the ECU, which is then relayed and causes the tachometer to start working erratically or sporadically.
Other common symptoms of a faulty crankshaft position sensor is lower fuel efficiency and the engine could run very rough, misfire before stalling out completely.
One way to check if your crankshaft position sensor is faulty is by using an OBD scanner and reading the error codes from the ECU. If you receive diagnostic trouble codes between P0335 and P0338, then your crankshaft position sensor is having a problem.
Although an OBD scanner might not help you pinpoint the exact issue, it’s still an excellent tool to narrow down the culprits.
#2. Faulty Engine Control Unit (ECU).
Another source of the problem that might lead to the car shutting off while driving and an illuminated Check Engine light is a faulty Engine Control Unit (ECU) or engine control module.
The ECU in your car is a computer that collects information from various parts of an internal combustion engine to make sure everything in the whole system is working properly in an optimal and precise manner to maximize efficiency.
A faulty ECU can cause sudden drops in power, fuel efficiency, and spark loss, causing your car to shut off randomly and turn back on. Another common symptom of a faulty ECU is your car stalling and jerking while driving. The check engine light might also light up on your dashboard.
Unfortunately, testing and inspecting your ECU is not easy. If you want to try troubleshooting yourself, the only thing you can do is to use an OBD scanner to see what diagnostic trouble code you get.
However, the code might still not be clear-cut for a failing ECU. Your only option is to take it to a professional mechanic. A mechanic will have the right tools and software to diagnose your ECU.
#3. Bad Alternator.
The alternator in your car is in charge of producing a constant stream of electricity from the car’s mechanical energy. It uses this electrical energy to run various electrical parts such as the dash lights, dome lights, conditioning unit, stereo, and to charge the battery.
If, for some reason, the alternator is not doing its job properly, your car will not get the electrical power it needs, leading to the problem of the car shutting off. When this happens, you will get a flashing dash.
It’s important to note that if your battery is functioning properly and can supply power after your alternator dies, your car can still run for a while without an alternator, so you might not realize right away what you’re dealing with.
But your car can only last a short period while running on the battery, as the battery is not designed to provide power to the entire car. Once your battery dies, your car will stall and eventually shut off completely.
If you pay enough attention to how your car runs, you should be able to sense when an alternator is not working properly; that is, your car will begin to receive an intermittent amount of power.
Regardless, a basic DIY car maintenance job is a necessity. Use a multimeter or a voltmeter to test your battery together with your alternator at regular intervals, say every 4-6 months.
To test an alternator, leave the engine running, turn off all lights, including the dashboard, and all accessories like the stereo that may be using electricity. Perform the battery test with the multimeter.
Then, test the alternator to see if it will function properly under heavy usage. Let the engine run at a speed of 2000 RPM. Turn on all accessories, including headlights, interior lights, radio, wipers … and reconnect the voltmeter.
A healthy alternator should produce between 13.1V and 14.6V at regular idle speed. Anything lower than 13.0 signals that it should be further inspected by a professional.
#4. Empty Fuel Tank but Faulty Fuel Gauge.
You might be surprised to learn that thousands of people find their car shuts off while driving due to an empty fuel tank.
While some might be too busy or forgetful to check the fuel level regularly and refill at the earliest opportunity, there are instances where your fuel gauge has gone faulty and does not show the real fuel level in the tank.
One of the common reasons for a faulty gas gauge is a sending unit failure. This will typically cause your fuel gauge to get stuck in one position regardless of the fuel level, which is typically at the “F” or “E” mark in most cases.
If you suspect that there is a problem with your fuel gauge or fuel level sensor, try to fill 1 gallon or 4 liters of gasoline to see if your car starts again.
#5. Clogged or Faulty Fuel Pump or Fuel System.
If your car stops while driving but then turns back on suddenly, it can often be due to a bad fuel pump. Your engine needs a precise supply of fuel at a precise time as input for combustion to generate power, and the fuel pump is the part that supplies the engine with the correct amount of fuel.
If the engine does not get the correct fuel amount at the right moments, the motor will shut off. And when this happens, it is very similar to your car running out of gasoline.
The bad news is if you are dealing with a faulty fuel pump, there is no bypass for it. You will have to fix it or replace it.
Another reason could be that your fuel filter got clogged. Over time, the filter can be clogged by contaminations in old gasoline, messing up the ability to produce power and causing your car to shut off.
If your fuel filter is nylon or paper, you should just replace it, which is cheap. If it’s made of metal, you can just clean and reuse it.
Most fuel pumps are installed inside the fuel tank. One quick way to check whether the fuel pump is really the culprit is to give the fuel tank a kick with your foot. If the car starts, there is most likely a problem with your fuel pump.
But do not do it violently with a metal tool, as the tank is made of plastic and you would not want to damage it.
#6. Bad Ignition Switch.
When you turn the key to start the car, the ignition switch, which is installed behind the ignition lock, gets turned. Inside the ignition switch are many tiny metal plates that can build up rust over time.
When this happens, one of these plates may lose connection, and the whole ignition will get switched off. Or the ignition relay can go bad, and the mechanism that controls the amount of electricity going through them will stop working.
All of these symptoms will cause the engine to shut off abruptly while driving.
Luckily, it’s easy to check whether a faulty ignition switch is the reason your car randomly shuts off. When that happens, check if there are lights on your dashboard.
If the dashboard instrument is dead, a faulty ignition switch is likely. Put your car keys in the ignition again after the car shuts down and try turning them. If this doesn’t start the engine, then you most likely have an ignition failure.
#7. Broken Spark Plugs.
A vital component that allows your engine to generate power is the tiny spark plugs. If you have only one faulty spark plug, you can still start your car and drive.
But when more than one spark plug malfunctions, your car may start, but it most likely won’t drive long. Multiple faulty spark plugs will cause your engine to stall and cut off while driving.
Before your engine completely shuts off and leaves you stranded, in most cases, there are other telltale signs that you should look out for, including reduced engine performance, lack of acceleration, engine misfires, and engine knocking.
If you come across these symptoms, it’s easy to locate and inspect bad spark plugs.
Once you can physically see your spark plugs, you can determine their condition. A bad spark plug is one that is blistered from running too hot, or one covered with a substance like oil, fuel, or carbon.
How To Fix A Car That Shuts Off While Driving?
If your vehicle shuts off while driving, the first thing you need to do to fix it is check the engine control module to see if it logged any error codes and recorded all sensor data. You will also want to ensure the car has fuel in the tank and that the alternator is working properly.
Here’s some more in-depth information on determining how to fix your car shutting off while driving problem:
#1. Check trouble codes.
With older car models, to diagnose whether or not the car has a problem, you needed a multimeter or some common sense.
Luckily, with modern vehicles, the car has built-in diagnostics that tell if ‘something’ is wrong. When it detects that one of the engine sensors has an issue, it stores a fault (trouble) code, which is also coupled with a check engine light on the dashboard.
This has made the diagnosing process much easier as you don’t have to waste time checking every sensor in your car’s engine, and you don’t have to guess and change the wrong parts before you find the issue.
So the best way to determine why your vehicle shuts off while driving is to check your trouble codes from the engine control module, and see if there was anything stored to show there was an issue.
If you want to read the fault codes, you will need to get hold of your own OBD2 scanner or take it to a repair shop that will. Bad spark plugs, the ignition coil, or the ignition system could cause a misfire trouble code.
#2. Check the Alternator Voltage.
If you do not have an OBD2 scanner or do not have any trouble codes stored, your next step is to check the alternator voltage with the engine on. You will want to engage the emergency parking brakes and start the engine to measure the voltage of the car battery using a multimeter.
If you have a voltage range below 12.5 volts, there could be an issue with the alternator or the charging system.
Here is an extensive guide on how to test your alternator: How to Test a Car Alternator (5 Steps)
#3. Fill the Fuel Tank.
It may seem elementary, but you should always be sure the fuel tank is filled up; you could also be low on fuel without even knowing it! Low fuel can cause the engine to stall when cornering at high speeds, as the pump starts sucking air instead of fuel.
Additionally, there is a possibility that the fuel gauge sensor in your tank is defective, and your fuel level is low even though your fuel gauge is reading full.
So, this is definitely something you want to verify by opening the fuel cap and putting a small amount of fuel in.
#4. Check the Fuel Pressure.
Another common cause of your car shutting off while driving is low fuel pressure, and you will want to check the fuel pressure in your vehicle. The easiest and most accurate way to check the fuel pressure is to use a manual pressure gauge connected to your fuel rail or line.
You could also use a diagnostic scanner to measure the pressure if your vehicle has a pressure sensor on it, but there’s always a chance this sensor could be faulty.
Check the fuel pressure specifications for your vehicle, and if you find that the fuel pressure is low, you should check the fuel filter, fuel pump, and fuel pressure regulator.
#5. Inspect the Tachometer.
The tachometer or RPM meter on your vehicle is telling you the information from the crankshaft position sensor in most vehicle types.
If your tachometer does not work when your vehicle shuts off, or if the tachometer needle does not move when you turn on the engine, the crankshaft position sensor has likely malfunctioned or the camshaft position sensor has malfunctioned.
#6. Check the Dashboard.
When your vehicle shuts off, the next thing to check is the lights on your dashboard. If the dashboard lights shut off when the vehicle shuts off, this might indicate a potential problem with the ignition switch.
This may also indicate low battery voltage, due to a defective alternator, as we discussed in step three. So, if that is the case, you will want to check both of those.
#7. Check Sensor Data.
If you can’t find any errors stored in the ECU memory, but you still have an issue with your vehicle, you will want to check all data from the engine sensors by performing an On-Board Diagnostic Test.
To check this data, you’ll want to use a diagnostic tool that is compatible with your vehicle’s Engine Control Module. It can be quite difficult to know what these sensors are supposed to show, so you’ll need to get a repair manual or the specifications for your vehicle first.
#8. Visit a Professional.
If you’ve tried everything in the previous sections and your vehicle still shuts off while driving, it may be reasonable to get a professional involved. If it costs a lot of money, it may be reasonable as well to get a professional involved who has most likely been through this situation many times before.
It is not guaranteed that visiting a mechanic will cost more either, if they can find the problem quickly and accurately, rather than replace all the wrong parts.
FAQs.
What should I do when the car shuts off while driving?
If you find yourself in a situation where the engine stalls while driving, the first thing you’ll want to do is guide the vehicle to the side of the road.
Next, pop the hood and make sure the engine oil level is okay.
Do not try to restart the car if there’s no oil on the dipstick or if the engine was making strange noises before stalling.
If everything looks okay, you can then try to restart the car. Call roadside assistance for a tow if your vehicle doesn’t restart.
Is a Car That Turns Off While Driving Safe?
Whether or not it’s safe to drive a vehicle when it’s intermittently stalling will depend on the vehicle’s hidden issues and the environment. If you suspect that there’s a problem with the vehicle’s fuel pump, then you shouldn’t continue driving in a remote location because you might end up stranded.
How Do I Fix a Car That Shuts Off While Driving?
As was mentioned, there are many different issues that could cause your car to die while driving. You (or your mechanic) will need to do some troubleshooting to determine the root cause of the problem.