## When I Put My Car in Park, the Engine Revs
Overview
When you put your car in park, you expect the engine to idle smoothly. However, sometimes the engine may start to rev or increase in speed. This can be a concerning issue, especially if you are unfamiliar with the cause. In this post, we will explore the potential reasons why your engine revs when you put it in park and provide some troubleshooting tips to help you resolve the issue.
Causes of Engine Revving in Park
There are several factors that can contribute to engine revving in park, including:
**1. Vacuum Leaks:** Vacuum leaks occur when air enters the engine through a hole or crack in the intake system. This can cause the engine to run lean, which can lead to increased idle speed.
**2. Throttle Position Sensor (TPS) Malfunction:** The TPS is a sensor that measures the position of the throttle valve and sends this information to the engine control unit (ECU). A faulty TPS can provide inaccurate readings, causing the ECU to adjust the idle speed incorrectly.
**3. Idle Air Control Valve (IACV) Issues:** The IACV regulates the amount of air that bypasses the throttle valve at idle. A malfunctioning IACV can cause the idle speed to be too high or too low.
**4. Transmission Problems:** In some cases, transmission issues can cause the engine to rev in park. For example, a faulty torque converter or a worn-out transmission mount can allow the engine to over-rev.
**5. Electrical Faults:** Electrical faults can also lead to engine revving in park. A loose or damaged wire in the engine control system can cause the ECU to receive incorrect signals, resulting in an unstable idle.
Troubleshooting Tips
To troubleshoot the issue of engine revving in park, you can follow these steps:
**1. Check for Vacuum Leaks:** Inspect the intake system for any visible holes or cracks. You can also use a smoke machine to identify any leaks more easily.
**2. Test the Throttle Position Sensor:** Use a multimeter to measure the voltage output of the TPS. The voltage should change smoothly as you move the throttle valve.
**3. Clean the Idle Air Control Valve:** Remove the IACV from the engine and clean it using a throttle body cleaner. Ensure that the valve is free of debris and that the plunger moves smoothly.
**4. Inspect the Transmission:** Check the transmission fluid level and condition. If the fluid is low or dirty, it should be replaced. Worn-out transmission mounts should also be replaced.
**5. Check Electrical Connections:** Inspect the wiring harness for any loose or damaged wires. Ensure that all connectors are properly seated.
Additional Considerations
* **Type of Vehicle:** Different vehicles have different idle speed specifications. Consult your owner’s manual to determine the correct idle speed for your car.
* **Engine Temperature:** The engine’s idle speed may vary slightly depending on the engine temperature. Typically, the engine will idle at a higher speed when it is cold and a lower speed when it is warm.
* **Aftermarket Modifications:** Modifications to the engine or exhaust system may affect the idle speed. Ensure that any modifications have been done by a qualified mechanic.
Conclusion
Engine revving in park can be caused by various factors, ranging from vacuum leaks to transmission problems. By following the troubleshooting tips provided in this post, you can diagnose the underlying issue and resolve it effectively. If the problem persists or you are unsure about the diagnosis, it is recommended to seek professional assistance from a qualified mechanic.
