Jan 15, 20215 min read

Reasons Your Engine May be Stalling.

Updated: Jan 16, 2021

-We expect as drivers to take our vehicle from point A to B and only turn off when you decide too. However, in some cases it doesn’t go as planned especially when your car ends up stalling out.

-It can happen either when driving normally, at higher speeds, or even when at a stop. Number one advice is DON’T PANIC for any of these situations rather make sure to bring yourself to safety before worrying about the car.

*Newer cars have more advanced computers so I would recommend buying any OBD2 scan tool so that you can find out if there are any codes that the ECU is giving that could be the cause for why your engine is stalling out.

Most Common Causes for Engine Stall Automatic Transmission

Situation #1 OIL and COOLANT Sensors

Lack of oil: If your car shows a “low oil” indicator while it’s stalling out or at any time please make sure to stop by somewhere safe and check and refill the engine oil as needed.

-One customer brought in a 2012 model Toyota Camry that was stalling out which only showed the oil pressure indicator while it was stalling. Once I checked the oil there was barely about 2 quarts in a 4.5 quart engine. After filling up the engine with fresh new oil, it has never stalled out since.

Lack of coolant: For more advanced vehicles, there are safety switches that cut off power to the engine if the car’s computer sees that the coolant temp is very high or level is very low in order to prevent your vehicle from destroying itself.

-Be sure to keep an eye on the instrument cluster once in a while so you can know if something is not right.

Defective Coolant Temp. Sensor: Your coolant may be at the correct temperature but the ECU cannot know this if the sensor is defective which would shut off the engine for safety.

Situation #2 LACK OF AIR

IACV or Throttle Body: Another cause for the problem in this situation could be the throttle body for cars with electronic throttle or the “Idle Air Control Valve” (IACV) for cars with a regular throttle (non-electronic) attached to the gas pedal with a throttle cable.........

-During idle, the electronic throttle is constantly readjusting to bring in the correct amount of air for efficient combustion.

Now, there are instances where carbon gets built up on the walls of the throttle body which therefore causes the throttle butterfly valve to get stuck which could therefore deprive the engine of air and therefore bring your engine to a halt.

This would also be the cause for your idle to be higher than normal as well.

-For cars with regular throttle, the IAC valve allows for the correct amount of air to mix during idle and if that is filled with carbon or defective, your car will either stall out or have a higher than normal idle rpm.

PCV and Vacuum Lines: If there is a leak in any of these lines, there is a chance that this can be your problem.

-Usually, if you have a small leak or the PCV is defective, you will notice that the engine would be unusually “rough” during idle. If these lines have a major tear, it is possible that your engine can stall usually at lower RPMs.

EGR (Exhaust Gas Recirculation): This is the valve that allows some exhaust gases to enter the intake to reduce emissions of harmful gasses such as NOx.

-When this valve is stuck in the open position, you will experience a rough idle as well as potential engine stalling

-A most common reason why the valve could be stuck is because of the built up carbon from exhaust gasses that had built up over time

-You can use throttle body cleaner and a soft brush to clean it either while attached to the vehicle (which would be more difficult to clean) or while removed from the vehicle which would help you to clean it thoroughly.

Situation #3 LACK OF ELECTRICITY

Alternator: If you see the voltage dropping in your vehicle or if your low voltage signs appear while driving and you know your battery is not that old, then most likely you have yourself an alternator that is in need of replacement.

This can in fact stall out your vehicle since it is not recharging your battery fast enough to supply power to the components that are essential for your vehicle to run (ignition coil, spark plugs, fuel pump, etc….)

Battery: If the battery’s voltage is dropping rapidly causing the engine to shut off, it may just be because your battery is just so worn out that it can’t hold in anymore charge…..

To find out if your battery is the culprit I recommend to either bring it in to Advanced Auto Parts or any other auto parts store that offers a free battery test. Or you can buy the battery tester online which does not cost much.

Spark Plugs: If your spark plugs are considerably worn out, the engine might only run for a few moments and then shut off.

-You will definitely feel a very rough idle and most likely seen the check engine light come on. Also, while driving you car may shake violently or very rough.

-After, checking the scan tool you may see multiple codes pertaining to cylinder (?) misfire. If so, then it is a good chance that your engine is not getting the correct amount of spark which would mean to replace the spark plugs and/or spark plug wires.

Situation #4 LACK OF FUEL

Fuel Pump: If your car stalls out when at higher engine load or when driving aggressively , a component that could be the cause of this is the fuel pump.

When the fuel pump is ready to give out, it won’t be powerful enough to supply the correct fuel pressure when at higher RPMs and so the fuel pressure drops and therefore deprives the engine of fuel which in fact stalls out the engine.

Fuel Injectors: Sometimes the fuel injectors may get clogged which could cause the air/fuel mixture to go lean at first and when it gets worse it would therefore deprive the engine of fuel and stall out.

-Fuel injector cleaners like Lucas Upper Cylinder Lubrication & Injector Cleaner can be poured into the fuel tank and be used to clean out the injectors. I've done it before and it definitely works!

Fuel Pressure Regulator: In some rare instances the fuel pump might not have any problems. However, when driving, the fuel pressure regulator may be defective which would not allow for the correct amount of fuel pressure in the fuel rails. This would therefore deprive the engine of fuel and force it to stall.

Situation #5 WRONG TIMING

Sometimes the timing belt may slip a couple teeth or maybe the mechanic you gave it to messed up the timing. Either way, wrong timing if often overlooked and could be the reason why your engine is shutting down.

-Hopefully this is not the case on your vehicle, because if the timing for your engine is not correct it could potentially damage the engine if it is an “interference engine.”

-However in “non-interference” engines there is a safety mechanism that does not allow the engine to destroy itself, even if the engine would potentially stall out or not start up correctly.

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