Most commonly that is due to a vacuum leak. Look for loose or cracked vacuum hoses. You can also spray water onto the engine while it is still cold to see if it gets sucked in anywhere.
Feb 10, 2014 at 2:14 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.