So car has been idling rough when it gets to arround 700 its revs up to like 1500 then drops and everytime it drops to normal idle it revs back up again. Ive changed all vacuume lines havent clamped the new ones so air may be slipping thru. What else would cause this idle. The car fires right up as soon as i turn the key no problem on 1 crank.

 

Thats a classic sign of a vacuum leak. I know you said you had changed the lines, but it sounds like one isn't plugged in. Make sure the one in the bottom of the intake plenum is plugged in and check the one going to the vacuum canister. I've got an 87 IROC but I figure your bird should have a similar setup. The line going to the canister had cracks that I couldn't really see until I removed it. Vacuum leaks are a royal pain to find. Best of luck to you.

 

I can not find the dam soarce of the leak, heres video of the car running. I know the one going to the vacuum canister is good and im not sure exactly which one u are talking about that goes under the intake plenum, any pics of where this one is?

http://www.youtube.com/watch?v=EYUHDS3Y8DY

 

Is this a sudden onset thing or has it been going on for awhile? Have you recently done any work under the hood?

 

I had a problem where it would struggle to idel at normal and keep trying to die unless i gave it gas. I changed my iac and o2 sensor and that went away but now its doing what is in the video idling at normal then reving then dropping back down and reving back up again. All ive done recently was change iac, o2 sensor and exhaust manifold gaskets.

 

OK. Here's a pic. This is the intake from the drivers side just below the throttle cable.

 

I think you forgot to attach the pics

 

Sorry bout that. Pic didn't upload the first time.

 

im gonna post some pics of how my lines are setup its only one tube going in not like yours.

 

This is from both sides of the plenum

 

Ok. If I see this right, yours just tees off on the opposite side of the intake from mine. No big deal. I'm guessing your vapor canister is on the passenger side. If that is the case, that explains why your lines look different, because mine is on the drivers side. The main thing is, the vacuum line is plugged into the intake. Have you done a vacuum test on your system yet? We could guess at this thing all day. Advance, autozone, pepboys, etc all carry vacuum testers. Usually pretty inexpensive. I think mine was $15. Let's see what your vacuum is first and go from there. It should be above 15 inches and hold steady at idle.

 

i will go pick one up as soon as i can and do a test

 

it does seem that after running for a while it starts to calm down on the reving a bit.

 

It will usually calm down a little when the engine warms up. Let me know how the test goes.

 

ok will do thanks. I need to get this solved soon man this is my daily driver and ive been carless for like 2 months now.

 

so i tested the vacuum and its jumping from 15 to 17 jumps to 17 or 18 when it revs

 

Even though you're staying above the 15" threshold, it still looks like you've got a vacuum leak. It should hold steady. I'm not an expert by any means, so hopefully some of the 3rd gen gurus will chime in at this point. You indicated that you changed all of the vacuum lines. Did you replace the hard lines as well as the large flexible rubber lines? The one that goes to the brake booster, etc.

 

well i didnt change all of them lol sorry bout that i just checked them and changed the ones that were cracked or weathered. I did replace the ones that are connected to the brake booster and the one going to the canister along with almost every other rubber hose i saw. I can hear air hissing out when i cut the engine but by the time i get back under the hood its gone so i dont know where it is.

 

Hmmm. If you can hear hissing then I would be willing to be you've got a line disconnected. For it to be loud enough for you to hear, it's not just a cracked line. Of course, we're assuming that's what the hissing sound actually is. Ok, have you checked the lines underneath the intake? One goes to the fuel pressure regulator and one to the EGR. You gotta stand on your head a little bit to see them. They are the small hard plastic lines.

 

havent checked those today was reconnecting exhaust which i now know why i always reaked of exhaust after driving. The dam thing was ghetto rigged and neither side connects flush. Theres gaps on both sides so i have exhaust leaking into the engine bay which makes its way into my car. Looks like i need to find some more miracle money for headers.

 

That sucks. Headers are just like women, you can live without'em, but who wants to?Good luck dude. Summit has some reasonably priced headers.

 

my friend that helped me with the exhaust was saying i can get rid of most vacuum lines that i have on the and just plug them up is this true? which lines are nessesary and which can be ditched.

 

I'm not going to say you can't,BUT!! You have to be fully aware of what you are removing. Removing a vacuum line is essentially turning off or on whatever it's plugged into. For example: If you unplug the vac line to the climate control, you can still get air but it will only blow through the defrost vents. If you don't know what will happen if you unplug it, don't. I seriously doubt that GM built an engine with a vacuum system just for the h*ll of it. It's your car, do what you want. If you don't get the results you want, smack your friend and make him plug everything back up.

 

lol nice answer i just have no idea if the lines are even plugged as they are supposed to be because he did say it looked to him like everything was routed completely different. Is there a guide anywhere that will show me how all the lines are supposed to be routed in an easy to understand way?

 

Here is a great thread that discusses your issue. Also do a search for emissions diagram.

https://www.thirdgen.org/forums/tpi/...ml#post4389233

 

i had a similair issue on mine twice. once was a bad seal on the intake gasket, and the other was a burnt valve. (both causing vacum leaks). i would go around the car with a can of brake cleaner with the car runing to try and find the leak instead of just throwing parts at it. then do a compression and leak down test. also gm ran two different iac valves. the is a difference between the maf cars and the sd cars. if it got better when you changed it you may want to pull the iac housing off and get it all nice and clean so it can seat right. if you can get it off and have some one bead blast it so they can get in were the ting seats it works best. good luck and dont give up on it you will get it!