i have a ford expedition when it is in drive and idling

There could be a couple of problems. The first one is a vacuum leak. A vacuum leak could cause this concern. These vehicles do have a problem with the pcv valve hose deteriorating and making a vacuum leak. The part that deteriorates is the elbow where it hooks onto the intake manifold. It is located towards the rear of the manifold. Follow the pcv hose/pipe from the right valve cover. The other possibility is the idle air control motor being dirty or faulty. If you get some throttle body cleaner you can remove the hose between the throttle body and the air cleaner. While someone keeps the engine running by giving it gas spray the cleaner into the throttle body and into the hole inside the throttle body that is before the plate. This hole goes to the idle air control motor and will clean the crude out of it. The crude can get sticky causing the motor to open to far making the idle surge as it opens and closes.

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