My symptoms were :

Idle would be fine when initially started up, around 1000RPM. Once hot could idle around 1200,1300RPM, soon after would start holding the RPM around 2500-3000 RPM (Which made it awesome to try and drive through town lol).

I pulled out the IAC valve, and found the little rubber cap at the end was sticky with carbon, and from what I gather, when it got hot, it would stick in the TB opening where it goes. I cleaned it with TB cleaning and cleaned it ports out in the TB. Since doing that, the idle is 100% normal, around 1000RPM when warm.

This is a pic of the IAC valve, in case anybody has same issues, this is where I would start as it worked for me :


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My car idles right below 1k unless I kick the heat/ac on and then the idle shoots up a couple hundred. Im gonna check this out now, thanks for the post!

 

Thanks for the info!!! My LS-1 was doing the same as yours!! I did as you said in your post and it is running fine now !!!! Thanks

 

Mine prolly idles at 700-800, and about 900 when heat or ac is on

 

Well spoke to quick -- did fine for a day or so -- now back to same thing!!!

 

hey guys i really need some help i have a 2001 trans am ws6. after market ls6 heads cam and intake stock throttle body. i am having idle issues. ive already changed IAC,TPS, temp sensor, cleaned throttle body checked for vacuum leaks ( not extensively ) replaced MAF with a buddies still same issue. ill start the car. as it warms up it will idle around 1100 rpm ( normal is around 800 rpm ) ill tap the gas really quick and the idle will shoot up and hang around 1500-2000 rpm. then after about 3-5 seconds it will drop back down to 1100 rpm. my next step is buying a throttle body seal and see if its leaking anywhere
all advice would be greatly appreciated
thanks!

 

Check for vacuum leaks; pay close attention to the EVAP and PCV hoses/lines.

 

alright i will do that today and see if i can find anything. any particular places or other things i should check/look for?

thanks!

 

still no luck at all tried 3 different tps sensors. no leaks from what i can tell. it wont relearn at all on scantool its acting like the tps isnt reading at all it say 0.0 to 0.3 but mosnty just stays at 0.0. its drivin me crazy !!

 

did this ever get solved anyone?? My car is doing this after a cam install. Starts up cold and idles good then i tap the gas and the idle jumps up to about 2300 rpm and stays there. Doesnt seem to be any vacuum leaks in the hoses anywhere. any help would be greatly appreciated.

 

Are you tuned? I put a new catch can on my cammed car, and I have a big cam. I accidentally cut a vac hose with a worm clamp. Completely torn in half. It idled at 950 vs 750. It did load up with fuel at wot, is how I noticed it.

Not 2000 rpm idle.

 

I did what you said and it worked!! Thanks for helping me fix this problem, car runs like new now.