Why Does My Car Stall at Idle?

Updated on May 18, 2020
Dan Ferrell profile image

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

A fault in one or more components or systems may cause your engine to stall at idle.
A fault in one or more components or systems may cause your engine to stall at idle. | Source

If your car stalls at idle, it may show a particular symptom before it shuts off. For example, your engine may:

  • hesitate
  • idle rough
  • surge
  • be hard to start
  • idle erratically

These symptoms may vary from one model to the next. But a particular pattern, or similar one, may point you to a potential source of trouble you can diagnose at home.

Often, the fault is not hard to find if you know what to look for. Usually, all you need is a simple diagnostic technique(s) and some common tools.

Listed below, you'll find different stall-at-idle patterns along with the possible fault to help in your diagnostic. So head over to the appropriate section that most resembles the symptom in your car. But keep in mind the other sections since symptoms may not only vary but change as a problem worsens. Specially, pay attention to those systems that haven't seen maintenance for quite some time.

And remember that the vehicle repair manual for your particular model is a valuable tool when dealing with an engine or another car system problem. Operating parameters and system configuration may differ from one model to the next. And you need the particular specifications and, sometimes, diagnostic procedure for your model.

If you don't have your manual yet, you can buy a relatively inexpensive copy from Amazon. Haynes manuals include step-by-step guides to help you troubleshoot, maintain, and replace components for many systems in your vehicle. So you can recoup your small investment soon.

Index
1. My Car Has Been Losing Power and Now It Stalls at Idle
2. My Engine Hesitates and Dies at Idle
3. My Engine Idles Rough and Sometime Dies After It Starts
4. My Engine Idles Rough and Stalls
5. My Engine's Speed Goes Up and Down and After a Few Minutes It Dies
6. My Engine is Hard to Start, Idles Rough and Dies
7. My Engine is Hard to Start When Cold and Dies at Idle
8. My Car Idles Rough and Stalls Almost Immediately
9. My Engine Idles Erratically and Sometimes Dies
VIDEO: Vacuum Leak Causes a Stall at Idle
10. My Engine Idle Speed Has Changed and Sometimes Dies
11. Dealing With Car Stalling Issues
Replace the fuel filter at regular intervals to prevent engine stall.
Replace the fuel filter at regular intervals to prevent engine stall. | Source

1. My Car Has Been Losing Power and Now It Stalls at Idle

This is a potential sign of a clogged fuel filter. Usually, you begin to notice the vehicle not responding well on the highway. You've begun to lose power. Then you notice the same symptom while driving within the city. Now the engine has begun to idle rough and stalls.

Maybe your fuel filter has clogged. Foreign particles like dirt, water, rust accumulate in the fuel filter element over time until proper fuel flow is prevented. Without proper fuel volume, the engine starves and dies.

Check your car owner's manual or vehicle repair manual for your fuel filter's service schedule. Usually, vehicle manufacturers recommend replacing the fuel filter every 12 or 24 months, depending on your particular model.

The fuel pump or fuel pressure regulator may also show the same symptoms. A worn or faulty fuel pump or fuel pressure regulator may fail to keep up with engine fuel demands. If necessary, check the fuel pressure regulator and fuel pump.

A clogged air filter can also cause an engine to stall.
A clogged air filter can also cause an engine to stall. | Source

2. My Engine Hesitates and Dies at Idle

Just like fuel, an engine needs the proper volume of air to operate. And just like a fuel filter, an air filter will clog over time causing airflow to drop. As power is significantly reduced, your engine begins to hesitate and dies at idle.

Usually, vehicle manufacturers recommend replacing the air filter every 30,000 miles (48,280.32 km). Consult your vehicle repair manual for the correct service interval for your particular application.

You can check the air filter just by holding it up against a light. If light barely gets through or not at all, replace the filter.

A faulty MAF sensor can send the wrong signal to the ECU and stall the engine.
A faulty MAF sensor can send the wrong signal to the ECU and stall the engine. | Source

3. My Engine Idles Rough and Sometime Dies After It Starts

Usually, a faulty mass airflow (MAF) sensor can trigger the check engine light, but not always.

The MAF sensor reports the amount of air flowing into the engine through the air cleaner assembly. The car's computer uses this information, along with data from other sensors, to calculate engine fuel needs. However, if the sensor is reporting incorrect data, it may cause the engine to stall.

Sometimes, you can diagnose a faulty MAF sensor with a quick test:

  1. With the engine off, pop the hood open.
  2. Start and let the engine idle.
  3. Tap the MAF sensor lightly with a screwdriver handle or similar tool.
  4. If idle seems to have improved, test the MAF sensor.

The previous test may not work all the time. If there's no difference at idle, but you still suspect the MAF sensor, troubleshoot it.

A bad MAF sensor may cause the engine to die soon after it starts.

Other possible symptoms may include:

  • rough idle
  • hesitation
  • surge

Dealing with a dirty MAF sensor:

The most common MAF sensor in used today has a hot wire as a sensing element. It is common for this wire to become dirty and fail to appropriately read the air density flowing into the engine.

If dirt has covered the sensing element, you can clean it using MAF sensor cleaner.

Usually, a bad MAF sensor will trigger the check engine light (CEL). If necessary, check the computer memory for potential trouble codes, even if the CEL is not on.

Remove carbon buildup from the throttle body using carburetor cleaner.
Remove carbon buildup from the throttle body using carburetor cleaner. | Source

4. My Engine Idles Rough and Stalls

Gum and carbon buildup can accumulate around the throttle body bore and under the throttle plate. This can cause the throttle plate to stick and falter as you depress the accelerator. The result is a rough idle and stalling condition.

Take a look at the throttle bore, around and under the throttle plate. If necessary, spray a shop rag with carburetor cleaner and use the rag to remove gum and buildup.

A bad or clogged IAC valve is a common source of engine stalling issues.
A bad or clogged IAC valve is a common source of engine stalling issues. | Source

5. My Engine's Speed Goes Up and Down and After a Few Minutes It Dies

The car computer uses the idle air control (IAC) solenoid valve to control airflow and adjust idle speed when the engine is idling.

But over time, carbon buildup from PCV and EGR system operation can accumulate around a throttle bore and plug IAC solenoid passages. Or the device itself may fail. This may cause engine to idle at high RPM or erratically and, occasionally, stall. Other times, you may notice idle speed has increased and won't come back down to its previous speed. This may be another sign of an IAC valve gone bad.

On most models, the IAC solenoid is readily accessible. Depending on your particular model, you may need to remove the air cleaner assembly. The IAC solenoid is mounted next to the throttle body.

Usually, all you have to do is unplug the solenoid's electrical connector and unscrew two mounting bolts to remove the device. Check the solenoid and throttle body air passages and remove buildup using carburetor cleaner.

If you suspect a bad valve, you can troubleshoot the IAC using a digital multimeter. If necessary, consult your vehicle repair manual.

If the PCV valve sticks open, it may cause the engine to stall.
If the PCV valve sticks open, it may cause the engine to stall. | Source

6. My Engine is Hard to Start, Idles Rough and Dies

The positive crankcase ventilation (PCV) valve directs crankcase vapors into the intake manifold to prevent these gases from escaping into the atmosphere.

It's not uncommon for this valve to stick open, allowing too much air to flow to the engine during idle. This will lean the air-flow mixture and cause the engine to idle rough and die.

On most vehicle models, the PCV valve is easy to access and remove. Usually, you can clean the valve using carburetor cleaner, but most vehicle manufacturers recommend replacing the valve when it fails.

You can troubleshoot the PCV valve at home. Most PCV valves are relatively cheap and can be replaced in minutes, when necessary. Consult your vehicle repair manual to locate and replace the valve.

A bad ECT sensor can report coolant fluid at operating temperature during a cold start.
A bad ECT sensor can report coolant fluid at operating temperature during a cold start. | Source

7. My Engine is Hard to Start When Cold and Dies at Idle

An engine that is hard to start when cold and dies at idle may be dealing with a faulty engine coolant temperature (ECT) sensor. On some models, the problem can be traced to a dirty throttle body, a faulty idle air control (IAC) valve, or even a vacuum leak as well.

The car computer takes information from the ECT sensor to deliver the proper amount of fuel to the engine. When cold, the engine needs a rich air-fuel mixture. When warmed, the engine needs a lean mixture.

But a faulty ECT sensor can upset the mixture. If the sensor reports to the computer that the coolant is at operating temperature when it's not, the engine will receive much less fuel than needed. You may notice the engine harder to start, idling rough and, in many cases, stalling.

Most fuel injected engines use an ECT sensor and an air temperature (AT) sensor. A bad AT sensor may cause the same symptoms when bad.

You can troubleshoot the coolant temperature sensor at home using a digital multimeter. If necessary, consult your vehicle repair manual to locate the sensor.

If the ECT sensor seems to be operating properly, check the AT sensor.

On some models, other potential problems may come from:

Carbon buildup can cause an EGR valve to stick open.
Carbon buildup can cause an EGR valve to stick open. | Source

8. My Car Idles Rough and Stalls Almost Immediately

Usually, but not always, this is a sign of a stuck-open exhaust gas recirculation (EGR) valve.

The engine uses the EGR valve to recirculate exhaust gases back to the cylinders to lower engine temperature and control the emission of harmful oxides of nitrogen (NOx).

On some vehicle models, the EGR valve is controlled through engine vacuum, others are electronically run through the computer, whiles other use a combination of both systems.

Normally, the EGR valve remains closed until the engine has reached operating temperature and a predetermined speed.

When the EGR valve opens, it connects the exhaust manifold to the intake manifold. Over time, these passages fill with carbon particles and harden, blocking the flow of gases. This is when you start having trouble starting and idling the engine. But the valve itself, or a component in the system may fail as well.

You can troubleshoot the EGR valve at home using handheld vacuum pump and test a solenoid using a digital multimeter. If necessary, consult your vehicle repair manual.

Check the MAP sensor, its electrical circuit and vacuum hose.
Check the MAP sensor, its electrical circuit and vacuum hose. | Source

9. My Engine Idles Erratically and Sometimes Dies

Some vehicle models use a manifold absolute pressure (MAP) sensor. This sensor measures atmospheric pressure and sends the appropriate signal to the computer, which uses this information and other sensors' data to control engine fuel delivery.

If the MAP sensor sends the wrong signal to the computer, it may cause the engine to idle rough and stall. A faulty MAP sensor may also cause engine speed to cycle up and down. A bad signal may come from a faulty sensor, a fault in the electrical circuit, or a disconnected or damaged vacuum hose in the system.

You can troubleshoot a MAP sensor at home using a vacuum pump and a digital multimeter. See your vehicle repair manual for more information.

The following video shows you how a damaged vacuum hose connected to the MAP sensor causes the engine to stall at idle.

Vacuum Leak Causes a Stall at Idle

Vacuum leaks can lead to engine stalling problems.
Vacuum leaks can lead to engine stalling problems. | Source

10. My Engine Idle Speed Has Changed and Sometimes Dies

Engine vacuum leaks are one of the common sources of engine idle trouble and, depending on the size of the vacuum leak, performance issues.

A small vacuum leak usually won't affect engine performance much, but you may notice an erratic idle and, if enough vacuum is escaping, a stall issue when the engine is running at minimal speed.

A small vacuum can be hard to find. There could be a small vacuum hose loose, unplugged, kinked, or damaged in some way. Also, the problem could be a leaking gasket.

You can use some simple techniques to troubleshoot for vacuum leaks at home.

Check common sources of engine stalling issues at idle.
Check common sources of engine stalling issues at idle. | Source

11. Dealing With Car Stalling Issues

Pattern symptoms of an engine that continually dies at idle may vary, as systems' configuration change from one model to the next, even if the fault comes from the same bad component. Still, you'll be able to recognize some the descriptions presented here.

Even more, a stalling issue may happen under different conditions:

If your diagnostic didn't turn out a particular fault, these other components have been found to be at fault under similar patterns as those described above:

Whether your vehicle stalls at idle, at stops, while driving or only when cold, it's a good idea to scan your car's computer for trouble codes. Even if the check engine light is not on. A pending code may give you a clue about the potential problem.

And consult the vehicle repair manual for your particular make and model. Your manual troubleshooting section can point you to a potential system(s) or component(s) you can check and do the necessary tests.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

Questions & Answers

    © 2020 Dan Ferrell

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      • hardlymoving profile image

        hardlymoving 

        3 weeks ago from Memphis, TN

        From my experience, could also be:

        * clogged fuel injectors

        * ignition wires shorting or going bad

        * clogged cat converter

        * PCM malfunction (burned out capacitors)

        * short in the wires leading to the electronic throttle body

        * electronic throttle body malfunction

        * coil packs sporadically working

        * engine ignitor malfunction

        * fault in the electronic gas pedal

        * fault in the clutched alternator

        * excessive carbon buildup on the intake valves of GDI engines

        * worn out piston rings

        * stretched timing chain

        * fault in the camshaft position sensor

        * leak in the intake manifold or plenum gasket

        * bad upstream O2 sensor(s)

      working

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