Highter Than Nornal Idle Due to Vacuum Leak on GMC 3500 Pickup

Problem Description and Possible Solution

An engine vacuum leak may develop from the throttle body gasket causing a higher than normal idle speed. Failed gaskets should be replaced.

Problem Data
RepairPal Verified
Average mileage: 48,860 (48,860–48,860)
Engines affected: 5.7L V8, Gasoline
11 model years affected: 1990, 1991, 1992, 1993, more1994, 1995, 1996, 1997, 1998, 1999, 2000
12 people reported this problem
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When you start the truck, the idle goes high, and when I put in drive, it comes to normal!!
What that could be?