What Causes A Car To Die While Idling?

It’s a nightmare come true when you are sitting at the stoplight and your car stalls. What does it mean when your car stops moving?

Defective oxygen sensors or mass airflow sensors can cause a car to stall when it idles. It can also be caused by an EGR valve that’s stuck open or fouled spark plugs. It could also be caused by an idle air control valve or throttle body, fuel pump, transmission, or fuel system. 

We will be discussing the possible causes that a car could die from idling. Also, we discuss the cost of each repair.

Índice de Contenido
  1. Idle: Car Stalls for Reasons
    1. 1. Mass Airflow and Defective Oxygen Sensors
    2. 2. Stuck Open EGR Valve
    3. 3. Fouled spark plugs
    4. 4. Throttle body
    5. 5. Idle Air Control Valve Malfunctioning
    6. 6. Problems with the Fuel System
    7. 7. Transmission Problem
  2. Diagnose an Idling Engine
  3. Stalling Engine Repair Costs

Idle: Car Stalls for Reasons

1. Mass Airflow and Defective Oxygen Sensors

Mass Air Flow Sensor

Many sensors monitor engine performance and ensure the right mixture of air and fuel. Each sensor sends information to ECM (engine control unit). The ECM uses this data to determine how the engine should be controlled for optimal operation.

It is located in the exhaust manifold. The sensor monitors the airflow to and from the engine. To measure the amount of air entering, the mass airflow sensor is located alongside the engine in the intake air conduit. 

This information is used to determine the required amount of combustion chamber air. Incorrect information from one sensor will cause the ECM to send the incorrect amount of air. This can lead to problems when the ECM is idling. 

2. Stuck Open EGR Valve

Egr Valve Location

Exhaust Gas Recirculation is the process of taking a small amount of exhaust from the combustion chamber and sending it back to the engine. This helps reduce the engine's internal temperature. The carbon dioxide doesn’t burn as oxygen does, so it’s able to reduce the temperature in the engine. 

If the EGR valve gets stuck open, the exhaust gas won’t stop flowing. Because of excessive exhaust, the ratio of air to fuel becomes unbalanced. The system may also be able to absorb more air. The engine will stall if it doesn't have the correct amount of power. 

RELATED: 6 Symptoms of a Bad EGR Valve (& Replacement Cost)

3. Fouled spark plugs

Sooty Spark Plug

The spark plugs have to ignite the air and fuel mixture that’s in the combustion chamber. The spark plugs become less efficient at initiating the ignition process as carbon deposits accumulate on their tips with age. This causes the engine to lose power, causing a slow idle effect. 

Regular maintenance includes changing the spark plugs. This is part of the routine tune-up. While copper plugs may last for only 30,000 miles but can be replaced with iridium and platinum plugs which will go up to 100,000 miles. 

RELATED: 6 Symptoms of Bad Spark Plugs (& Replacement Cost)

4. Throttle body

Install Throttle Body

If your car was built before 2000, the mechanical throttle body will probably be present. Airflow may be impeded if these are contaminated or dirty. It can cause a engine to stop working.

Electronic throttle bodies are standard equipment in cars made after that date. If there’s a problem with the circuitry or connections, a defective throttle body can cause the engine to stall. 

A dirty throttle body could be the cause. For more information, please refer to the article.

RELATED: 8 Symptoms of a Bad Throttle Body (& Replacement Cost)

5. Idle Air Control Valve Malfunctioning

Idle air control valves or actuators keep the RPMs within the correct range especially while the engine is idle. The actuator uses the ECM information to calculate the correct RPMs. 

The engine's speed could drop if the valve or actuator is damaged. If the speed drops to too low, it can cause engine to stop. The idle air control valve will be integrated into an electric throttle body if it has one.

6. Problems with the Fuel System

We have discussed the need for the proper amount of air in the combustion chamber, but it’s equally important that there’s the right amount of fuel. If there’s a lack of fuel getting to the engine, the car could stall. 

Many components of the fuel system could be at fault. It could be a problem with the fuel pump or fuel filter. Other symptoms can also be caused by fuel system problems. There may be whining or surging, and you might have difficulty starting your car. Performance decreases and the engine is more efficient. This means you'll spend more time filling up the tank. 

7. Transmission Problem

It is not something anyone wants to hear. The transmission could also cause problems with idle. 

Problem here is the torque converter. A torque converter functions as an automatic transmission's clutch. The motor's power is transferred to the torque converter. The torque converter can become locked up if it is damaged, worn out or becomes unusable. The resistance causes the motor to stall. 

There’s also the chance that it is just the solenoid. It is the electromagnet that regulates and measures fluid pressure. 

Diagnose an Idling Engine

These are the steps to help you determine the root cause of your problem.

  1. Diagnose trouble codes. To check if there are any errors, use your OBDII Code scanner. Find the cause of the error and fix the problem to get rid of the code.
  2. Apply some fuel fluid to the throttle body. This will indicate a fuel system problem if your vehicle does not run normally. 
  3. The fuel pressure should be checked. Install a fuel pressure sensor in the pressure end of your fuel delivery system. For a gasoline engine, expect to see between 40 and 50 PSI. Diesel engines often have higher pressures. You can find the appropriate reading in your vehicle’s service manual. 
  4. Test for spark. Use an inline ignition tester to test for spark. Turn the engine on. The engine should light up if it is getting a spark. You should inspect the spark plugs. 
  5. The throttle body should be cleaned and calibrated with the OBD2 scanner if you have this option. To calibrate your throttle body, you may have to visit your dealer.

If these steps don’t help you find out what’s wrong, you might need a professional to take a second look. 

Stalling Engine Repair Costs

Repairing a stalling motor will cost you differently depending on its condition. For parts and labor, expect to pay between $150 and $500 if you need to install a new oxygen sensor. You can expect to pay between $200 and $350 to replace your mass airflow sensor. 

It could run $250-$400 to replace an EGR valve. You may be able clean your EGR valve for as little as $150 or $200. However, the issue may not be solved and you will have to replace it. 

Cost to change the spark plugs will vary depending on which type of ignition system you use. A complete tune-up can cost you between $50 and $250. A platinum or iridium sparkplug will allow you to drive your car for up to 100,000 miles between service intervals. 

It’s possible that you can clean the throttle body and resolve the issue. The only thing you need is throttle body cleaner. If there’s a circuitry issue, you may need a new throttle body, which could cost $200 to $650. 

Realized: Cleaning a throttle body (10 Easy DIY Steps)

The cost to replace your air control valve could be anywhere from $100 to $500. A fuel pump replacement can be costly, at $200 to $1,000. However, a fuel filter will only cost $50 to $200. 

The transmission is where the biggest problems are. It could run $600-$1,000 to replace the torque converter. However, if it’s just the solenoid that needs replacement, you could spend $15 to $100. Plus, this job is easy enough to perform yourself, so there’s no reason to pay for any labor.

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