Car Engine Shuts Off When Stopped

Introduction

If your car engine shuts off when you stop, it can be a frustrating and dangerous problem. There are a number of potential causes for this issue, and it’s important to identify the cause in order to fix it.

Causes of Engine Stalling

Idle Air Control (IAC) Valve: The IAC valve is responsible for controlling the engine’s idle speed. If the IAC valve is faulty, it can cause the engine to stall when you stop.
Throttle Position Sensor (TPS): The TPS tells the engine’s computer how far the throttle is open. If the TPS is faulty, it can send incorrect signals to the computer, causing the engine to stall.
Mass Air Flow (MAF) Sensor: The MAF sensor measures the amount of air entering the engine. If the MAF sensor is faulty, it can send incorrect signals to the computer, causing the engine to stall.
Vacuum Leak: A vacuum leak can allow unmetered air to enter the engine. This can cause the engine to run lean and stall.
Fuel Pump: The fuel pump supplies fuel to the engine. If the fuel pump is faulty, it can cause the engine to stall.
Fuel Filter: The fuel filter removes impurities from the fuel. If the fuel filter is clogged, it can restrict the flow of fuel to the engine, causing it to stall.
Spark Plugs: The spark plugs ignite the air/fuel mixture in the engine. If the spark plugs are worn or fouled, they can cause the engine to stall.
Ignition Coil: The ignition coil provides the spark to the spark plugs. If the ignition coil is faulty, it can cause the engine to stall.

Troubleshooting

If your car engine shuts off when you stop, there are a few things you can do to troubleshoot the problem:

Check the IAC valve: The IAC valve is located on the throttle body. It is usually a black or gray solenoid with a vacuum hose attached to it. To test the IAC valve, start the engine and let it idle. Then, unplug the vacuum hose from the IAC valve. If the engine speed increases, the IAC valve is faulty and needs to be replaced.
Check the TPS: The TPS is located on the throttle body. It is usually a black or gray sensor with a three-wire connector. To test the TPS, start the engine and let it idle. Then, slowly open and close the throttle. The TPS voltage should increase smoothly as you open the throttle. If the TPS voltage does not increase smoothly, the TPS is faulty and needs to be replaced.
Check the MAF sensor: The MAF sensor is located in the intake duct. It is usually a black or gray sensor with a three-wire connector. To test the MAF sensor, start the engine and let it idle. Then, unplug the MAF sensor. If the engine speed increases, the MAF sensor is faulty and needs to be replaced.
Check for vacuum leaks: Vacuum leaks can be difficult to find. However, there are a few things you can do to check for them. One way is to use a smoke machine. A smoke machine will fill the intake system with smoke, and any leaks will be visible as smoke escapes. Another way to check for vacuum leaks is to listen for hissing noises. Hissing noises can indicate a vacuum leak.
Check the fuel pump: The fuel pump is located in the fuel tank. To test the fuel pump, you can listen for it when you turn the key to the “on” position. You should hear the fuel pump running for a few seconds. If you do not hear the fuel pump running, it may be faulty and need to be replaced.
Check the fuel filter: The fuel filter is usually located under the hood, near the fuel pump. To check the fuel filter, you can remove it and inspect it for dirt and debris. If the fuel filter is clogged, it needs to be replaced.
Check the spark plugs: The spark plugs are located in the cylinder head. To check the spark plugs, you can remove them and inspect them for wear and fouling. If the spark plugs are worn or fouled, they need to be replaced.
Check the ignition coil: The ignition coil is located on the engine. To check the ignition coil, you can remove the spark plug wires and inspect the coil for cracks or damage. If the ignition coil is cracked or damaged, it needs to be replaced.

Repair

Once you have identified the cause of the problem, you can repair it. Here are some tips for repairing the most common causes of engine stalling:

IAC valve: The IAC valve can be cleaned or replaced. To clean the IAC valve, remove it from the throttle body and spray it with carburetor cleaner. Then, use a cotton swab to clean the valve seat. To replace the IAC valve, simply remove the old valve and install the new one.
TPS: The TPS can be adjusted or replaced. To adjust the TPS, loosen the bolts that hold it in place and turn the TPS until the voltage is correct. To replace the TPS, simply remove the old sensor and install the new one.
MAF sensor: The MAF sensor can be cleaned or replaced. To clean the MAF sensor, remove it from the intake duct and spray it with MAF sensor cleaner. Then, use a cotton swab to clean the sensor element. To replace the MAF sensor, simply remove the old sensor and install the new one.
Vacuum leak: Vacuum leaks can be repaired by replacing the damaged hoses or gaskets. To find the vacuum leak, use a smoke machine or listen for hissing noises.
Fuel pump: The fuel pump can be replaced. To replace the fuel pump, drop the fuel tank and remove the old pump. Then, install the new pump and reconnect the fuel lines.
Fuel filter: The fuel filter can be replaced. To replace the fuel filter, simply remove the old filter and install the new one.
Spark plugs: The spark plugs can be replaced. To replace the spark plugs, simply remove the old plugs and install the new ones.
Ignition coil: The ignition coil can be replaced. To replace the ignition coil, disconnect the spark plug wires and remove the old coil. Then, install the new coil and reconnect the spark plug wires.

Conclusion

If your car engine shuts off when you stop, it can be a frustrating and dangerous problem. However, by following the steps outlined in this article, you should be able to identify the cause of the problem and repair it.