I just put a LS6 intake on my 00 Z and once i started it, it kept a high idle when rolling. Like between gears it would stay at around 2k. So i thought I pinched a gasket and replaced them and it still does the same thing. It might not be quite as bad but that could be in my head. It doesn't do this everytime but pretty often. Sometimes if you just throw the clutch in it will stay on say 1500 to 1700. Is it possible its the throttle position sensor or does it sound like a vaccumm leak?

 

Sounds like a vacuum leak somewhere to me. Check for any cracked vacuum lines while you were swapping the intake. I doubt it's the TPS, but you can check it easily with a DMM and some pieces of guitar string. Back-probe the TPS connector using the guitar strings, then sweep KOEO while connected to a voltmeter to rule out any TPS malfunction.

 

definetely sounds like a vacuum leak

 

Sounds like a vac leak. Mine would surge bad after i did my intake. Turned out my my pcv setup was disconnected and hanging behind the motor due to a cracked elbow on the passanger side head nipple that slide back there. hooked it back up and the high surging idle went away, got a tune and now its gold. Def would check all your pcv lines and make sure they are hooked up according to the diagram under the hood

 

Welcome to the club bud. Mine does the same exact thing after I put on the FAST 92/92 combo. I spoke to Thunder Racing about it (thought maybe it was the Fast TB acting up) because my tuner didn't notice anything after the install/dyno tune. My tuner said he checked for leaks and couldn't find any. Gene @ Thunder said he believe's it's in the tune. I'm taking the car back soon to see if I can pin-point what exactly is going on. Other than it doing it once and a while, it drives amazing w/ no surging or bucking.

 

vacuum leak would make the car run bad! it would surge and even cut off. try removing the battery for more than 10 mins to reset may be? it happened to me in the past and it solved it.

 

Did you tighten the intake bolts in the specified 2-step sequence at 44 and 89 in/lb, or go by feel?

New intake gaskets or re-use the old ones?

 

I know this is an older thread, but Im replying because of the part about the tightening sequence. I dont have the high idle just a noise.

But after removing and putting my stock LS2 intake back on I noticed a "sucking/whistling" sound when I hit the gas. Only when you step the gas rather hard, and only when its under load, and only at the beginning. As rpm's rise it goes away. I checked all the hoses/fittings with propane and carb cleaner with nothing. Then pulled the intake tube and put smoke in through the throttle body and the only place that leaked was my catch can. So I took the can off and put the factor hose back on and I still hear the noise!!

Only when I put the intake back on it was about 45 degrees out and didnt use the correct sequence or torques and just hand tightened them. I didn't put on new gaskets either. Could this be the problem? Does that make that big of a difference? Im really running out of things to try. I plan on taking the intake off and putting it back on "correctly" tomorrow. Think this is the problem? Should I pick up new gaskets?

Thanks in advance!

 

inspect your current gaskets and see if they are worn. i didnt bolt my intake to the correct specs but at least do the pattern which you can find on ls1howto.com if everything is correct then it must be a gasket leak..good luck!

 

I dont know if this applies to you, but I had the same issue after a removal and reinstall of my intake manifold. Turns out my cruise control cable was holding my throttle body open. Weirdiest thing... unhooked it and it was normal. I dont know WTF it had wrong with it. I dont use it anyway, so it's unhooked for good.