2. Clean the throttle body. The throttle body is a valve that controls the amount of air that enters the engine. If the throttle body is dirty, it can cause the engine to idle too high. To clean the throttle body, remove it from the engine and spray it with a throttle body cleaner. Be sure to clean all of the passages in the throttle body, including the idle air control valve.
3. Check the idle air control valve. The idle air control valve is a device that controls the amount of air that bypasses the throttle body. If the idle air control valve is faulty, it can cause the engine to idle too high. To check the idle air control valve, remove it from the engine and test it with a multimeter. If the idle air control valve is faulty, it should be replaced.
4. Check the fuel pressure. The fuel pressure should be within the specifications listed in the vehicle's owner's manual. If the fuel pressure is too high, it can cause the engine to idle too high. To check the fuel pressure, connect a fuel pressure gauge to the fuel rail. If the fuel pressure is too high, the fuel pressure regulator should be replaced.
5. Check the spark plugs. Spark plugs that are worn out or have the wrong gap can cause the engine to idle too high. To check the spark plugs, remove them from the engine and inspect them for wear or damage. If the spark plugs are worn out or have the wrong gap, they should be replaced.
6. Check the ignition timing. The ignition timing should be within the specifications listed in the vehicle's owner's manual. If the ignition timing is off, it can cause the engine to idle too high. To check the ignition timing, use a timing light. If the ignition timing is off, it should be adjusted.
