Could have a large vacuum leak, egr stuck open, or a leak after the mass airflow sensor. Try disconnecting the mass airflow sensor and see if it idles.
February, 9, 2010 AT 1:26 AM
Look at your cars throttle position sensor and idle air control valve. These two will make the car hard to start or not start at all because it was located in the general area of the intake manifold right where the throttle cable connects. Hope it helps.