Car Shuts Off While Driving

Has your car been running really rough? Is the idle of your car not smooth as it should be and it occasionally stalls?

There can be a tenfold of reasons, including worn-out electrical parts, faulty battery, failing alternator, and fuel system problems to highlight a few.

The car shuts off when idle and always restarts with no check engine light, and no codes can be infuriating.

Having a basic knowledge of the makings of your car can really help you counter stalling at the idle problem.

I am about to shed some light on the issue with respect to my own experience, and what other drivers in the automotive community have to say.

What Would Cause a Car To Die While Driving or Idling?

An engine that has a tendency to stall can die suddenly when you are cruising with your car, or when acceleration is necessary.

Therefore, stalling should not be taken lightly. If you drive one of the cars involved in safety evaluation, get it to a dealer.

If you have a different model or make, find out what is causing the stalling and fix the issue. There’re many deficiencies that contribute.

Faulty Crankshaft Position Sensor (CKP)

The crankshaft position sensor is used by the ECM to establish the precise position of the pistons in the engine.

It monitors the rotational speed as well as the position of the crankshaft and transmits the data to the engine control unit for the necessary adjustments with respect to operating parameters.

The crankshaft position sensor is the primary sensor for measuring engine speed and most of the ECM table reference engine speed.

So, with a faulty crankshaft position sensor, your car simply will not start, or it can intermittently start or fail to start.

A crankshaft position sensor that works intermittently can set misfire codes followed by backfires through the intake and exhaust.

What You Should Do

The most popular signs of a faulty crankshaft position sensor that can be a cause of your car idling low and cutting off are:

  • Intermittent stalling
  • Problems starting the car
  • Check engine light
  • Vibration in the engine
  • Slow accelerator response
  • Erratic starting
  • Misfiring of the cylinder

The most ideal course of action when you have established that the CKP is the problem is to replace it with a new one simply.

Now, changing the CKP is generally not that difficult – one or two bolts maybe and a connector. Unbolt it or unplug it, and usually, you’re good to go.

Failing Fuel Pump

There has to be some kind of motive force to push the fuel into the intake runners. This force is delivered by the fuel pump.

The fuel pump has to be capable of supplying sufficient fuel with enough speed to meet the demands of your engine without the supply pressure in the fuel rail dropping.

There are no compromises when it comes to the fuel pump. It is the one thing that ensures your engine never runs out of gas.

So, the slightest issue will surely result in major drivability problems. And in extreme cases, your car will simply not start.

What You Should Do

Check for the common signs of a failing or weak fuel pump, which can include any or all of the following:

  • Engine not starting
  • Difficulty starting
  • Whining noise from the tank
  • Misfire
  • The decrease in power and acceleration
  • Poor fuel efficiency

There are a number of things you can check to confirm a failing fuel pump, and they include: fuel pump noise, loosen/misplaced timing belt, clogged fuel filter, and wet fuel pressure regulator.

Before you consider replacing the fuel pump, you can conduct a fuel system pressure diagnosis by using a fuel pressure gauge.

High fuel pressure readings usually suggest a faulty pressure regulator or an obstructed return line.

Low pressure can be the result of a clogged fuel filter, defective fuel pressure regulator, weak pump, or restricted fuel line.

Replacement cost for a fuel pump may vary from three hundred to one thousand US dollars with respect to your car make and model.

Failing Alternator

Modern cars come equipped with a highly efficient and compact alternator. This part of your car is accountable for the supply of electricity.

If a car engine shuts off when idle, then your car may have a failing alternator. A defective alternator will limit power supply to important parts of your car.

What You Should Do

Look out for major signs of a failing alternator, such as:

  • Engine losing power abruptly
  • Dashboard warning light
  • Headlights flickering or dimming
  • Battery runs down
  • Rough running

Check the condition and tension of the drive belt at every oil change. Also, keep your battery and alternator connections clean.

If the problem persists, take your car to a local mechanic for a quick fix. However, if you have experience working with other car systems, you could easily fix or replace the alternator.

Faulty (ECU) Engine Control Unit

If you have a modern car, it has the engine control unit or ECU. This is a small computer that controls almost everything that is associated with your engine functionality and performance.

The ECU detects the accelerator pedal position as well as the current operating states of your engine by means of sensors.

The computer collects data on-road speed, air mass intake, charge air pressure, fuel rail pressure, and crankshaft speed and angle, among other things.

What You Should Do

Check for signs of a failing, faulty, or bad engine control unit (ECU), which can include any of the following:

  • Check engine light
  • Engine shuts off when idle
  • Engine misfiring or stalling
  • Bad fuel economy

As much as you would like to fix everything in your car, fixing or replacing a failing engine control unit is not within your expertise.

You have no choice but to hire a professional mechanic who will conduct a detailed diagnosis and come up with a fitting solution.

Problems with the Ignition System

Your car’s ignition system is responsible for generating a timed spark and supply it to the cylinders of your engine.

The ignition system plays a vital role in turning the engine on & off.

The produced spark is supplied to the spark plugs where it jumps the gap and ignites the air-fuel mixture just before the piston reaches the top of its compression stroke.

Your car shuts off while driving electrical problem can be due to a weak spark that causes poor combustion and lack of power.

What You Should Do

Look out for signs of a bad/faulty ignition relay and/or coil, which can include any of the following:

  • Car turns off
  • Car won’t start
  • Unresponsive ignition
  • Engine misfiring
  • Car stalling
  • Backfiring
  • Rough idling or jerking of the engine
  • Engine hard starting
  • Check engine light or DTC code

You can easily change or replace the ignition relay or ignition coil on your own. You just need to know the correct piece to replace. Alternatively, you can hire a professional to do a surefire job.

Faulty Idle Air Control Valve

The idle air control valve works with your car’s ECU to electrically regulate airflow to ensure smooth idling.

According to research, millions of car makes and models have a faulty idle air control that will need to be replaced soon.

When the idle control valve malfunctions, you are likely to face all kinds of problems with your car when idling. In some extreme cases, your car’s drivability may be hindered.

What You Should Do

Look out for the common signs of a bad, faulty, or failing idle air control valve, such as:

  • General solenoids failure from everyday use
  • Wear and tear from corrosion
  • A clogged valve
  • Stalling when the engine is idling
  • Car shut off while idling and won’t start
  • Rough or unsteady idling
  • Extreme RPM drops during the slowdown

You might probably need a replacement if you have a clogged valve or worn out the valve from corrosion. For this service, you will need to hire a professional mechanic.

Just make sure the valve you are getting ensures proper airflow to your engine during changing load requirements.

Empty Fuel Tank

This is an obvious cause when your car randomly shuts off. You need to periodically check the dashboard to confirm the number of miles you have until your tank runs dry.

Forgetting to refuel is not an option, not unless you want your car shut off while driving and won’t start.

Final Words

If your car turns off when stopped, this is no ordinary issue. The most obvious suspect would be the faulty crankshaft position sensor.

However, as we have seen, your random stalling or sporadic stalling may be caused by other issues, as well.

You might be having a failing fuel pump, a failing alternator, a faulty engine control unit, a weak ignition system, or a faulty idle air control valve.

There’s always more than one thing to look out for, especially when the check engine light is on. If you have no idea what you’re doing, it is always a good idea to see a professional mechanic.

Alex Schandert

Cars are judged on their honesty, practicality, quality and value for money, not on their nought to sixty times, or whether they induce over-steer at the limit, whatever that is. I've loved cars since I got my first car, an old Toyota Tacoma when I was Eighteen. I'm always happy to share my experiments by publishing product guides, reviews, and useful tips.

4 thoughts on “Car Shuts Off While Driving”

  1. I recently changed my 02 sensors and when driving to get my car inspected, the car would stall every time I was coming to a stop. It would stall and the steering wheel would lock up. This did not happen prior to me changing the 02 sensors. Is this a normal problem?

  2. The bottom line is, you’re better off with a simpler 1980s car that can still be fixed at home. Those dependants on garage services shall drain your bank account.


Leave a Comment