If your car dies while driving and then restarts, you probably will think that a huge mechanic repair bill is on the way, but that’s not always the case.
I have a 2007 car that used to die while driving and then restarts as if nothing happened. I was afraid of a huge mechanic repair bill, so that’s why I had to figure out on my own what was causing the problem. It turned out to be a faulty fuel pump, but there are also many things that can cause your car to die while driving and then restart. Here are the top reasons why your car dies while driving and then restarts:
Why My Car Dies While Driving And Then Restarts
- Faulty Fuel Pump
- Engine Misfire
- Bad Cam Position Sensor (Error P0340)
- Faulty or Failing Mass Airflow Sensor
- Vacuum Leak
- Faulty Throttle Position Sensor
Why My Car Dies While Driving And Then Restarts
Here are the top reasons why your car dies while driving and then restarts:
1. Faulty Fuel Pump
A faulty fuel pump can cause your car to die while driving and then restart on its own. The thing with most vehicles is that a faulty fuel pump will not throw a check engine light because there are parts of the car that the computer system doesn’t know anything about. One of the big things that most car computers don’t know about is the fuel pressure because there’s no sensor on many cars to tell the computer what the actual fuel pressure is.
So, if the fuel pump starts to go bad, the computer isn’t going to know what the fuel pressure is, and it often won’t set a code. Your car will continue to die once in a while and then restart on its own. So, checking the fuel pressure is the first thing you should do.
How to check the fuel pressure:
- Get a fuel pressure testing kit. I got one from amazon.com and you can check it out here. It has a lot of different fittings and works on all models.
- Choose the right adapter from the fuel pressure testing kit.
- Connect the adapter to the fuel line bolts into the fuel rail.
- Connect that line to your gauge to measure the pressure.
- Start the engine and leave it to run at idle.
- On idle, the fuel pressure should be between 46 and 49 psi
When you don’t have enough fuel pressure, the car won’t run right, especially at higher speeds. It’ll just die when you go on a higher speed and then restart.
2. Engine Misfire
An engine misfire can cause your vehicle to die while driving and then restart on its own. A severe misfire will prevent a vehicle from running properly. Every time the spark plugs ignite the fuel in the cylinder and move the piston down as a result, that’s going to speed up the reluctor ring.
The reluctor ring is attached to the crankshaft and every time there is combustion in the cylinder, the reluctor ring is pushed just a little bit. This movement is monitored by the vehicle computer. In case of an engine misfire, there is not a sudden burst of energy that is going to move the reluctor ring and the vehicle computer is going to know that there’s something wrong with that cylinder and can cause your vehicle to die while running and then restart. This will also trigger a misfire engine light.
The engine could misfire due to:
- a faulty ignition coil
- faulty fuel injectors
- low engine compression
- oil on a spark plug
- bad valve cover gasket
- tube seals open
- damaged wires
- worn spark plugs
- bad spark plug cables
- vacuum leaks
3. Bad Cam Position Sensor (Error P0340)
If your car dies while driving and then restarts on its own, it could be because of a bad cam position sensor. In order to check if your cam position sensor is bad, you will need a scan tool (you can get one on amazon.com).
How To Check For a Bad Cam Position Sensor and Replace It
- Connect the scanner to your car computer and turn the scan tool on. If the scan tool shows an error code P0340, you have a bad cam position sensor and it is making your car die and then restart while driving.
- Locate the cam position sensor. On most vehicles, the cam position sensor is located on the backside of the engine and it looks exactly as in the image shown above.
- Once you locate the cam position sensor, start your vehicle and keep it running.
- Grab a rubber hammer or a steel hammer wrapped with a cloth and gently hit the cam position sensor. If your car dies while you do this then your cam position sensor is bad and you need to replace it.
- Get a new cam position sensor on amazon.com for your vehicle made and model.
- Take out the old cam position sensor by removing the two bolts (usually a 10-millimeter socket).
- Spray the connector with an electrical cleaner. They only use tiny amounts of electricity, and any little piece of dirt will make them work incorrectly.
- Install the new cam position sensor and tighten the bolts, but don’t overdo it because the cam position sensor is made out of plastic and you don’t want to crack it.
- Scan your vehicle with the scan tool. You will probably see an ”check engine light” and you will have to restart it before starting the car again.
4. Faulty or Failing Mass Airflow Sensor
A mass airflow sensor is supposed to measure the amount of volume and density of the air getting drawn into your engine. The mass airflow sensor is then going to send out a little signal that goes out to the car’s computer and it’s gonna say you need to match this amount of fuel to this amount of air. That way the vehicle can run efficiently because it will have a proper air to fuel ratio.
The accuracy of the mass airflow sensor is going to be critical to making sure that your engine runs properly. If the mass airflow sensor gets dirty in any way or even damaged, it’s going to cause an issue with the run ability of your vehicle and your vehicle will die while driving and then restart itself.
You can unplug the airflow sensor and if the vehicle starts right up then the airflow sensor is faulty. Sometimes an airflow sensor can be saved by cleaning. Use an appropriate airflow cleaner (check prices on amazon.com) and clean the airflow sensor. In addition, inspect the inlet tube for possible cracks.
5. Vacuum Leak
A vacuum leak is any amount of unmetered or unmeasured air that enters your engine past your mass airflow sensor. In other words, any amount of air that enters your engine past the mass airflow sensor is not going to be measured and your vehicle’s computer will not know the exact amount of air that entered your engine. This will create an imbalance in the air-to-fuel ratio and can result in your car dying while driving and then restarting again.
The mass airflow sensor measures the amount of air that enters your engine and sends out that information to the computer so the computer can calculate and send the exact same amount of fuel to the engine. All of your engine’s vacuum lines, intake manifold gasket, air hoses, or any other type of air hoses need to be in good shape and airtight so they don’t allow any unmeasured air to enter the engine past the mass airflow sensor.
6. Faulty Throttle Position Sensor
A faulty throttle position sensor can cause your car to die while driving and then restart itself. The throttle position sensor is attached to the throttle body and measures the movement of the throttle body. As you press the gas pedal, the throttle body opens and the sensor tells the main computer how wide the throttle body is open so it knows how much fuel to fire with the fuel injectors.
A faulty throttle position sensor can send faulty data to the main computer and the main computer can then send too little or too much fuel causing the engine to die while driving. You will be able to restart your vehicle and the problem can reappear further down the drive.
How To Check For a Faulty Throttle Position Sensor
Here is how to check if your throttle position sensor is faulty:
- Hook up an OBD scanner to your vehicle’s computer. If you don’t have an OBD scanner, you can get one on amazon.com.
- Open the menu on the OBD scanner and select the option to measure the throttle position.
- Locate the throttle position sensor in the engine bay. It is usually attached right to the throttle body.
- Press the gas pedal couple of times to make the throttle body move.
- Check the data on the OBD scanner and see if the throttle position sensor has recorded any movement at all.
- If there is no movement recorded, your throttle position sensor is bad and has to be replaced with a new one.