Why your car engine is stalling and how to fix it

Your car engine stalling in the middle of the road can be so annoying, but this article will show you how to fix it when it happens.

Car engine stalling is a situation whereby your car stops occasionally when you don’t have any plan to stop the car. And this scenario can be so frustrating, especially in heavy traffic like Lagos traffic. The problem of engine stalling while driving is often associated with temperature. It can happen when you first start a cold car engine or even in chilly weather. Here, let’s take a look at various cases of car engine stalling and their causes.

man checking under the bonnet

When your engine stalls, open the hood and have a look at the spark

1. Car engine stalling once cold after it is started

If your car engine stalls, it usually means enough fuel is not getting to the engine or there’s too much air. An engine that’s cold requires a reasonable quantity of fuel mixture before it can start, though not running, while the engine warms up. Car engine stall problems can be caused by the following.

  • A dirty or faulty airflow sensor

When a sensor becomes soiled by dirt or fuel vanish, it will affect the performance of your car engine. There will be a delay in the way your car reacts to changes in airflow. Of course, it will hurt the fuel mixture. When it happens, there might be a shook up in the fuel mixture which will result in car engine stalling, idling and delayed problem. Using aerosol electronics cleaner to clean the airflow sensor wire, will revive activity and also solve the problem.

  • A faulty idle speed control system

Idle speed on an engine injected by fuel can be regulated when you let little air pass through the throttle. If there is fuel varnish or dirt in your engine’s idle air bypass circuit, or there’s a broken solenoid valve, there may not be enough air for the car engine to idle smoothly. This will often result in a car engine stall. It now becomes necessary that you clean the idle bypass circuit (found in the throttle body) with aerosol throttle cleaner. This will solve your car engine stalling problem. And if the aerosol throttle cleaner does not solve the stalling problem, then have a look at the wiring connector. It might have loosened. If you do not see any wiring fault, know it’s time to replace your engine’s idle speed control solenoid.

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car engine

Cleaning the idle bypass circuit in the throttle will solve the engine stall problem

  • A leak in the engine vacuum

Check to see if the vacuum hose is loose or broken, leaks at ERG valve and around the PCV valve, and also leaks around the body of throttle or the intake manifold gasket.

Video: Here’s how to find a vacuum leak

  • Low engine compressor

An engine that has lots of miles and a low compressor owing to a worn out piston ring or cylinder means there are one or more valves leaking. Having a look at the compressor will let you know if a problem has occurred or not. It will also tell you if the problem can be easily fixed or have the engine replaced.

  • A fouled or worn out spark plugs

Any car engine can stall or delay when the ignition misfires. When an engine runs slowly, there isn’t much momentum to keep it moving. An ignition misfire may cause the car to stall. In case there’s been no change of the spark plugs in a while, changing the old bad spark plugs and replacing it with new plugs or plug wires can do wonders. A hot spark will be restored while the ignition misfire fixed.

broken spark plug

Replacing the old spark plugs it with the new ones can do wonders

  • A bad manifold absolute pressure sensor (MAP)

The MAP sensor checks the intake vacuum which is used by the PCM to ascertain engine load. If the reading gotten from the map sensor is not accurate, the PCM may end up adding more or less fuel which will make the car stall.

  • A defective air temperature sensor

And talking about the PCM, the PCM needs to have the right input to enable it to balance the fuel mixture well. The air temperature sensor does the job of telling the PCM the air temperature that goes into the intake manifold. If the air temperature sensor is faulty in the same vein as a coolant sensor, it will screw up the air/fuel mixture. And of course, cause a car engine stalling problem.

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wires in a car engine

The air temperature sensor does the job of telling the PCM the air temperature that goes into the intake manifold

  • A defective coolant sensor

If the engine has been detected by the coolant sensor to be running colder than normal, it will enable the engine to run smoothly. And no cold stalling to that effect. However, when the engine heats up, a rough idle may arise which will consequently kill the fuel economy of the car. Another scenario can be when the coolant sensor detects that the engine has become warmer than normal or it regularly heats up. The car will stall when the engine becomes cold. This is because the PCM is leaning out the fuel mixture repeatedly. Having the defective coolant replaced will be the solution to the car engine stalling problem. This problem is a reason why you should not ignore your car’s engine coolant.

>>> Also check out: 7 most common types of sensors in car engine

2. Car engine stalling when you stopped at the traffic

A car idle stall always means the engine’s idle speed is too low. It can also mean the air conditioning compressor may cause the engine to lug down, because of a load it has created on the engine. Another meaning can be the fuel mixture is quite rich or not much, affecting how the engine runs-poorly. Here are some factors that may be responsible for this kind of car engine stalling.

Cars waiting for the green light

Your car stalling in traffic could be dangerous

  • An unusual electrical load high on the charging system.

When the battery runs down with the alternator finding it difficult to recharge the battery, the load increased on the engine will likely pull the idle rpm down to the level where it will cause the car engine to stall. Check the state of the battery to know if it has run down. Use a battery charger if the battery has gone low. You can also drive for 30 minutes or so on highway speed. If the battery still fails and can’t hold any charger, then know it’s time to get a new battery.

  • A bad air conditioning compressor.
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When the A/C compressor in the car engine binds up, it could be as a result of an Internal wear, inadequate lubrication or AC system that’s been overcharged. It may pull down the car engine when it’s being used. But if the engine problem only happens when your car’s A/C is on, the compressor has developed a problem.

3. Car engine stalls suddenly while driving

This kind of car engine stall is often associated with the ignition and occurs when the car engine loses spark. The reason for such a stall is often a faulty crankshaft position sensor. And sometimes, it can happen when the engine has just one coil.

When your engine stalls, open the hood and have a look at the spark. To do it, pull off a plug wire (that is if the engine has one), place the end beside a block, and have someone help you crank the engine. Mind you: Don’t hold the wire if your ignition system is still working, or else it may shock you. When the engine cranks and you don’t hear any sound of the wire snapping, the fault should be traced to the ignition system.

The front of a BMW

This kind of car engine stall is often associated with the ignition