Clean the throttle body. A dirty throttle body can also cause the idle to be high. The throttle body is located on the intake manifold and controls the amount of air that flows into the engine. To clean the throttle body, remove the air filter housing and spray the inside of the throttle body with a throttle body cleaner. Use a clean rag to wipe away any dirt or debris.
Check the idle air control valve (IACV). The idle air control valve controls the amount of air that bypasses the throttle body and enters the engine. If the IACV is faulty, it can cause the idle to be high. To check the IACV, disconnect the electrical connector and start the engine. If the idle drops, then the IACV is faulty and needs to be replaced.
Check for a faulty coolant temperature sensor. A faulty coolant temperature sensor can cause the engine to run rich and cause the idle to be high. The coolant temperature sensor is located on the intake manifold. To check the coolant temperature sensor, disconnect the electrical connector and start the engine. If the idle drops, then the coolant temperature sensor is faulty and needs to be replaced.
Adjust the idle speed screw. If none of the above solutions work, you may need to adjust the idle speed screw. The idle speed screw is located on the back of the throttle body. To adjust the idle speed screw, turn it clockwise to increase the idle speed or counterclockwise to decrease the idle speed.
Note: If you are unable to find a vacuum leak, clean the throttle body, check the IACV, check the coolant temperature sensor, or adjust the idle speed screw, you may need to take your car to a mechanic for further diagnosis.**
