Very unlikely this engine has an idle screw. These went away with the old fashioned carburetor.This engine more than likely has electronic fuel injection. With electronic fuel injection the engine idle speed is regulated by the engine management computer and is not adjustable.If you are having idling problems it is more than likely some problem with the engine.When was the last time it had a tune-up? It may be due spark plugs, spark plug wires and an air filter.Are there any modifications made to the engine? Maybe an after market part like a cold air kit was installed and the installer eliminated or forgot to reconnect an essential sensor.Your Idle Air Control (IAC) valve could be dirty and sticking or it could be malfunctioning. Remove the IAC valve and clean it and the port with carburetor cleaner. Bring the valve to any major auto parts store and have it tested. NOTE: You can not run the engine without an IAC valve so you will need to use a different vehicle to bring the valve to the parts store.Your fuel injectors could be dirty. Your fuel filter could be dirty. When was the last time your fuel filter was replaced? It should be replaced every 1 to 2 years.You could have a vacuum leak. Look for any broken, rotted, or disconnected vacuum hoses.If the change in idle was sudden, you could simply have gotten a tank of bad fuel. If the idle problem could go away the next time you fill up.Has there been any significant change in performance or fuel economy lately. You could have a mis-fire. A dead cylinder will take away at least 25% of your power and cause noticeable problems with the idle.