I have a 2000 silverado with the 4.8 and like most needed to replace the knock sensors. what should have been an easy fix turned into a 3 day project and now that it's all back together something isn't right. I read somewhere that the truck would need to relearn how to idle after cleaning the throttle body so I used that procedure and it didn't work. It's idling around 1100 rpm's, and when I approach a stop light its just trying to take off on me. I torqued down the intake manifold to 89 inch pounds so I'm almost certain that it couldn't be sucking air under the manifold. Anyways I'm lost! any help would be appreciated!

 

First, did you replace the intake gaskets or re-use them? If they are new gaskets, double check the intake tube where it bolts to the throttle body. Its very easy to seat the seal wrong and create a leak. Lastly I'd check the pcv tubes, purge valve and brake booster hose for proper installation.

 

Sounds like an intake leak to me. Check the brake booster hose to make sure its hooked up. And check for leaks like mentioned above.

 

kinda sounds like a leak to me toounless you messed up your IAC valve, or your throttle body cable stuff(the little black tensioner piece).. I would just check all your eletrical connections and if you dont see any visible intake leaks, get a can of throttle body cleaner and spray it around your hoses and intake gaskets.. if the idle rises then that is where your leak is..

Keep us posted.

 

Did you ever figure it out? Have the samething happening to me, except I didn't take my motor apart. I just went to the store and when I got home and pit it park it never idled down. Cranked it this morning and still idling around 1700 rpms.

 

On a friend's 01, it was idling at like 2000 and it was something in the IAC wiring because a new IAC would not fix it. We just unplugged the IAC and adjusted it by hand until it idled around 600rpm. Put it back together and left it unplugged. We are going to probe into the wiring one of these days and fix it. But it runs fine as is now.

 

Sounds like an IAC issue. What ever you do, don't cycle it when it it is out of the TB, it will go flying across the garage, and you will need to get another one. Ask me how I know. Lol