well i bought this car about a month ago now and it was running perfect when i got it...other than some cam surge every once in a while...well starting around 2 weeks ago the idle started moving on up daily to be higher and then leveled out at 1900 rpm exactly...then around 3-10 seconds later it will SLOWLY start going back down to the 950 desired idle....ive used carb cleaner to TRY to find a vacuum leak and no luck...since i was an lt1 guy before this i know absolutely nothing about the vacuum system on these cars...i know that the two 90 degree connectors for vaccum lines on the passenger side valve cover are both capped and the line that goes from the intake manifold to the throttle body is still there but a bolt is shoved in it to cap them off...also the throttle body does have the enlarged hole of 3/16's...im tired of this..it sounds ridiculous at stop lights and such having such a high idle! constantly sounds like i dont knwo how to drive a stick and revving it too high haha...please help me with this im so stumped

 

could make sure the intake manifold bolts are tightened down, the throttle body is snug against the manifold, the connections in the back of the manifold are plugged in tightly, the throttle body idle position screw might need a little adjustment, it could be any of a number of things. The only thing you know for sure is that unmetered air is getting into ur engine somwhere, so that means after the MAF. Some pics would probably be helpful, of ur setup in general and the psecific places you have capped off.

 

There's a chance it could be in the tune as well. Idle tuning can be a hard thing. One day it's right, next day out of wack.

 

So your valvecovers are completely capped off and there's a line from the manifold to the TB? This is about as bass ackwards as I've ever seen.


Where are the crankcase gasses escaping? Is there a breather somewhere?

Our cars have tables in the PCM that allow the RPMs to hang at a certain RPM until a certain speed, but since it just started, I doubt it's tuning. Sounds like that "bolt" he put from the TB to the manifold is leaking by now and air is getting past the throttle body. This is causing the car to idle high and the IAC (idle air control) motor to close off to compensate. This takes a few seconds, which would explain the brief idle hang and the RPM's slowing down.

You could take the IAC motor out and clean it. It's the top driver side sensor on the TB. You could also cap off the line on the manifold and the line on the TB properly. Advance Auto sells 3/8" vacuum caps a dime-a-dozen.

 

yes the line from the tb to the intake manifold is like a complete uturn and has something shoved in it to shut it off....and yes i have a breather on the oil cap position ill take better pics after work today

 

http://img481.imageshack.us/img481/9880/enginefg5.jpg

 

also dont most ls1 guys never descreen the maf??? i know i did on my lt1 but this one was already done and yes the car is tuned btw if someone asked

 

ok well i had enough time before work real quick

that one is capped with something in it like a piece of rubber
that one is capped with a screw? lol
the screw in the one to the tb from intake mani and you can also see that the bend is too much for the line and so it kinks and folds over
the bulge from the bolt and my overly priced snap on box

 

wow are you serious! Get some F'in vacuum caps, its like 3 bucks at autozone for a package of them. It will seal them properly, i can almost promise you this is your issue.

Ditch that hose too and just cap those ports off too.

 

LOL @ that setup. Whatever open hoses you have you need to cap off properly.