Car Engine Running After Turned Off

Causes

Idle air control valve (IACV): The IACV regulates the amount of air that bypasses the throttle plate when the engine is idling. If the IACV is stuck open, it can cause the engine to continue running after the key is turned off.
Throttle position sensor (TPS): The TPS sends a signal to the engine control module (ECM) that indicates the position of the throttle plate. If the TPS is faulty, it can send an incorrect signal to the ECM, which can cause the engine to continue running after the key is turned off.
Vacuum leak: A vacuum leak can cause the engine to run lean, which can lead to a high idle speed. If the vacuum leak is large enough, it can cause the engine to continue running after the key is turned off.
ECM: The ECM controls the engine’s operation. If the ECM is faulty, it can send incorrect signals to the engine’s components, which can cause the engine to continue running after the key is turned off.

To diagnose the cause of a car engine running after turned off, you will need to perform the following steps:

Check the IACV: The IACV is located on the intake manifold. To check the IACV, you will need to remove it from the intake manifold and inspect it for any damage or debris. You can also test the IACV by applying 12 volts to the terminals and listening for a clicking sound.
Check the TPS: The TPS is located on the throttle body. To check the TPS, you will need to use a multimeter to measure the voltage between the terminals. The voltage should change as you move the throttle plate.
Check for vacuum leaks: To check for vacuum leaks, you will need to use a smoke machine. The smoke machine will produce a smoke that will be drawn into any vacuum leaks. You can then use a flashlight to locate the vacuum leaks.
Check the ECM: To check the ECM, you will need to use a scan tool. The scan tool will allow you to read the ECM’s codes and data. The codes and data can help you to diagnose the problem.

Once you have diagnosed the cause of the problem, you will need to repair it. The repair will vary depending on the cause of the problem.

IACV: If the IACV is faulty, you will need to replace it.
TPS: If the TPS is faulty, you will need to replace it.
Vacuum leak: If there is a vacuum leak, you will need to repair it. The repair will depend on the location of the leak.
ECM: If the ECM is faulty, you will need to replace it.

There are a few things you can do to prevent your car engine from running after turned off:

Keep your car well-maintained: Regular maintenance can help to prevent problems from developing.
Avoid driving in extreme conditions: Extreme heat or cold can put stress on your car’s engine.
Don’t turn off your car while it is in gear: This can put stress on your car’s transmission.

By following these tips, you can help to prevent your car engine from running after turned off.