Chevrolet Repair: Idle adjustment - 7.4 Liter Fuel Injected, intake manifold gasket, vacuum leaks

Question
How do I adjust the idle speed on a 1996 7.4 liter fuel injected chev engine.  Why would the idle suddenly be so high? (approx. 2000 rpm) I cannot kick it down and it does not return to normal after it has warmed up.  
Thanks a bunch
Brad

Answer
The idle speed is controlled by the PCM (computer)and is non-adjustable.

First check for any trouble codes. Is your check engine light on?

Problem could be a vacuum leak or sticking throttle plates.
After engine warms up manually push the throttle lever on the throttle body and see if idle returns to normal. If it does return to normal the throttle plates are sticking.

Check very closely for vacuum leaks.

These are 2 of the most common causes, anything else will require further diagnosis.

There is a campaign on some 7.4 engine for a distorted upper intake manifold gasket. #96047
Call you Chevy dealer with the VIN and have the service advisor look up any recalls or campaigns for your vehicle. Recalls and campaigns are under warranty as long as you own the vehicle.