What Causes a Car to Rev Without Pressing the Accelerator?

[MacTanner]

The reasons why a car revs without pressing the accelerator: 1. The throttle cable is not returning to position due to insufficient lubrication. The solution is to remove the cable and pour lubricating oil from the upper end, allowing it to slowly penetrate into the cable tube. 2. The idle motor is stuck or has lost its memory. The solution is to clean or replace it and then re-learn it, which requires using a diagnostic computer for initialization settings. 3. If it's an electronic throttle, the throttle position sensor may be damaged. In this case, the throttle position sensor needs to be replaced. 4. Excessive carbon buildup in the throttle. This situation requires cleaning the throttle. 5. The accelerator pedal is stuck when returning. The solution is to readjust the accelerator pedal.