Used the search with no luck finding a duplicate problem. I don't have my car with me, so I can't check it right away. Just looking for things to check.

So here is what it's doing: Idle hangs and will stay high after driving. The car will idle perfect at start up though. Stop to get gas, it's at 2200 at shut off, start up after, 800. It will hang up at 3k and then drop some when I come to a stop. Sometimes it's at 1200, other times it's at 2300 and anywhere in between. Car will push you down the highway.

I noticed that my engine already has the internal PCV cover and it's is capped off. The external one is also still on the car, so that is going away, parts ordered already. Also will check out my map sensor first thing when I get back to the car. Not sure if that is it though, since it will idle normal sometimes. Car is speed density btw. The intermittent thing is what really has me scratching my head. Any ideas... I'll try them all.

Brent

 

Maybe make sure the idle air valve is not gummed up

 

I'd look for a vacuum leak.

 

Quick question about the vacuum leak. What really has vacuum lines? At a glance I don't even see any vacuum lines. Would a vacuum leak cause such variation?

 

I was thinking about this last night. There are two different versions of the LS6 valley cover -- only the 2004 has the actual internal PCV. The 01-03 still requires the use of an external valve. The only way to check is the part numbers which are inconveniently stamped on the underside; you'd need to pull the intake and valley cover to check.

So, what I think you should do is order that plug and hose that I mentioned. Remove the stock system, plug the valve cover grommet, take the cap off the tube on the valley cover and put it on the passenger side-rear tube (you'll still run the hose from the top of the throttle body to the front tube on the passenger side) and then run that new, small hose from the valley cover to the manifold where the PCV system currently plugs into. If that takes care of everything, then I'd surmise you're good to go.

With that said, you may want to ensure the intake manifold is A) tightened correctly in the proper sequence and torque spec, and B) ensure the manifold gaskets aren't junk. I only mention this stuff since we know it had a FAST on it for a bit.

As for the other vacuum lines, there would have been some off the AIR system to the back of the manifold. There is also a vacuum line running to behind the passenger strut tower for the HVAC system (which is also pulling vacuum from the back on the manifold).

IMO, you need to bring that car to my place some weekend and we need to get rid of the AIR system and just pull the intake and clean things up.

 

I was thinking about the possible intake leak myself. It would be a real pain driving all that way with the car pushing me down the interstate. I need to get that idle fixed before i come out and brain rape you. How much time are you going to have Akron weekend? Not much i figure...

 

I have a similar problem at present, my IAC 'stepper motor' for some reason is getting stuck in the 'in position' causing the engine to idle high, starts up cold fine.
Drive somewhere & after around 5 mins I can feel it pushing & idle hangs up around 2k plus.
I have to take it out of the TB, twist & pull the shaft out, re-install & all is well.
Not sure what's causing this, maybe my aftermarket ecu!

 

OK, so I finally got my PCV parts and got back up home to install them and see if that made any difference. Simple swap, only took about 5 mins to eliminate the outside PCV system, plug off the valve covers and install the loop to the valley cover. Also did a quick look at all the vacuum lines that I could see.

After install I took a test drive to see if it made any changes to the high idle. It sure did, it got way worse. So for whatever reason, I decided to cap off the TB and valley cover and try again, that seemed to help put the car back to the way it was before the install. So that doesn't fix my issues, but at least it also seems the PCV wasn't my problem.

Next, I pulled the lid off to see how the throttle body looked and clean it out. Ding Ding, a light bulb went off for an idea that I had before, but for whatever reason never tried it. After cleaning everything since I was in there, I put the lid back on and fired up the car. It always idles normal at initial start up, but after a crack of the throttle, back up to 1500+ she is. Next, I unplugged the TPS and wala, within a few seconds she's is idling normal. Plug it back in and back up it goes to 1600. Picked up a new TPS for $22 and had it installed in a few minutes.

Took the car out for a drive and she is perfect, idle drops right back down and car engine brakes now like it's supposed to. I just love the engine brake between shifts when driving normal, it's my favorite sound and even better now that it's the first time I've heard the car do it.

I wanted to thank you guys for the responses and post a solution to my problem so it wasn't left open ended.

Quick question, is there any issue with leaving the PCV stuff capped? I do have a breather on my oil cap, so I think I may have had redundant systems. Thoughts?