2000 Silverado 1500, 5.3 with 60k miles. I've owned this truck about a month now and while on a trip this weekend the idle became erratic to the point that it stalled out a couple of times when stopping at a traffic light. Now the truck doesn't stall out any more but will not idle down immediatley. It drops to about 1000 rpm then takes about 5-10 seconds to drop back to the normal 500 rpm. If I set still in neutral and burp the throttle the same results, takes about 5-10 sec to drop back to normal. It hasn't set the check engine light so there shouldn't be any codes, right? I've cleaned the throttle body (2 times), but that didn't help. It didn't appear all that dirty, very little residue, so I didn't remove the TB to clean it due to the coolant being routed through it. Thanks for any help

 

It could be your IACV.

 

The 5.3 engine is famous for the intake gaskets to fail causing idle problems. It may or may not set a code. I have never had to replace the IAC valve on a Chevy truck and performance problems are what I do everyday at work, that is not to say yours is not bad and I do see new things everyday. There is a 90% chance yours needs intake gaskets.I have replaced more than I can count. Be sure to get the gaskets from the dealer because they have been updated because of this problem. The new gaskets should be green the old ones are orange.

 

air leak somewhere. probably intake gaslet. or throttle body.
get a can of carb cleaner, put straw in, and start giving shots of cleaner following gasket's perimeter. when engine starts choking, you found the spot.