When your engine stalls, it's not only bothersome, it can cause unnecessary wear to your car, or it can even be dangerous. A stalled engine can keep your vehicle from moving effectively through traffic which can create a dangerous condition which could result in an accident. Diagnosing the cause of a stalling engine can seem like a complicated job, but the truth is that all modern engines operate on the same basic principals. That means that they all share the same common systems which could result in a stalling engine. Before attempting any diagnosis, it's a good idea to remember the last time you were under the hood for any reason (including something as simple as checking the oil or other fluids) and look around that area in the engine compartment for any connectors or parts that you could have displaced. You may find your fix right there. In a situation which requires a more complicated fix, the three most common culprits are:
A Faulty Sensor or Electrical Component
Modern engines rely heavily on electrical sensors to function properly. When an electrical component isn't working properly, the engine's computer isn't receiving the necessary information to keep the car running the way it should, which can result in a stall. Usually if an electrical component is to blame, the car's "check engine" light will be illuminated. A good first step to finding out what might be to blame is to pop the hood and check all the electrical connectors you can see. The problem might be as simple as a sensor that has become unplugged. If that's not the case you may have a sensor that needs replacing. You can take your car to a trusted repair shop, or many neighborhood auto parts stores will perform a free diagnostic check on your computer to help find the problem.
A Leak in the Car's Vacuum System
"Engine Vacuum" is another system that provides important information to your car's computerized management system. Locate the car's vacuum lines, and look them over, checking for unplugged connections, as well as signs of wear and cracking. It can be helpful to take a look at them with the vehicle's engine running so that you can listen for whistling or hissing sounds indicating a leak. While the car is idling the vacuum is at its maximum, so any leaks will make plenty of noise. Touch and move each line gently and listen for changes in the way the engine sounds, being careful of the engine's hot or moving parts.
A Leak or Obstruction in the Car's Intake or Fuel System
Anything affecting the engine's ability to take in air or fuel will cause the car to stall as well. With the car running, have a friend abruptly press and release the throttle (gas) pedal. Look that the hoses that connect the engine to the air box, where the filter is located. Any signs of collapse in the hoses or excessive air noise may indicate a problem with the intake. Check all the connections to make sure they are properly fastened. It's also a good idea to check or replace the air and fuel filters, because plugged filters are a common culprit as well.
Related Questions and AnswersCan Issues with the Engine Vacuum Gauge Lead to Engine Stalls?
Since the engine vacuum gauge is actually a piece of diagnostic equipment, it is highly unlikely that this will be the cause of your engine's stalling. It's possible that there is a problem with a MAP sensor (manifold air pressure sensor) or a barometric pressure sensor. More than likely, though, if you are using a vacuum gauge, you are looking at the vacuum in each cylinder to see if there might be a ring seal or valve seal problem. If that is the case, you will find that while it does take some work to put in a new ring or valve, it is fairly straightforward and you can save a bundle doing it yourself.Can a Faulty Electric Engine Control Unit Shut off the Engine Randomly?
Each Electronic Engine Control Unit is meant to operate in two modes. One is normal and the other is limp mode. If you can get your vehicle started at all, then the ECU (microcomputer that controls the engine) will look at the operating parameters and decide whether your engine should operate in limp mode. Unless there is a major-league short in the wiring leading to the ECU, it is highly unlikely that your engine will shut off randomly. Instead, it is likely the engine light will come on and you will be able to limp to your local dealer.What will Happen with a Dirty Diesel Engine Filter?
If your vehicle has a dirty diesel engine filter there are several possibilities. First, your engine will run very roughly, if you manage to get it started at all, and your vehicle will spew bright blue emissions smoke. If the filter is so dirty that fuel will not pass through, then the engine won't start, and the only way this vehicle will get to the shop is on a ramp truck. If the filter lets your car start and run reasonably without the emissions, then you will see your mileage drop like a stone. The famed edge in diesel economy will be gone.