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Discussion Starter #1
I have a hunting idle very little but it's there and I dont know where I could have the leak at. I'm on an aftermarket intake fs werks to be exact...for those of us who do have this intake there is a vacuum line underneath the intake elbow I dont know if theres a crack in it or something....I'm gonna try the old carb cleaner trick.
 

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The most common leak is on the pcv line. Standing over your engine looking down at it on the front right side behind the exhaust manifold there is a rubber 90 degree elbow. If its a vaccum leak 95% of the time it will be that rubber elbow. It will be contaminated with oil, torn, and collapsed on itself.
 

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Yeah, the most assured way of diagnosing that one is to remove it IMO. If you can easily crush the elbow, then it will collapse. If it's collapsing, then you won't be able to find it using any spray stuff trick. I prefer the starting fluid trick myself- but using either starting fluid or carb cleaner is not easy to do. The change to rpm is very, very, very slight, and half the time you don't know if you've actually done it or not.

The line that goes to the intake is the oil breather. It should go from the air intake to the valve cover. I don't really consider that one to be vacuum, but I'm not sure about the technical stuff. To me vacuum lines are after the throttle body (manifold vacuum)- not before.

To test your theory on that one, simply disconnect it from the air intake, and plug the air intake. You can also plug the side going to the valve cover---or (I just thought of this) at idle you should be able to feel manifold vacuum on that line if it's connected to the valve cover and the PCV is working as designed. Manifold vacuum is strong enough at idle to feel. If you can't feel it, then either the PCV itself is stuck closed, it's line is collapsed, or there's another large vacuum leak somewhere like the brake booster check valve.
 

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He needs to be on the Xcal loaner program and maybe a datalog will give a better idea where to look?

Can you take a lit cigarette and hold it next to vac leaks and maybe see them pull or push the smoke away?
 

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I had a similar problem last year, which was correctly diagnosed by Sailor on this forum....
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Posted via FF MobileNOT a common malady for our cars, but that WOULD cause a vacuum leak that is a typical cause of your issue as noted in prev. posts... PCV hose running under the intake could make it SEEM like a gasket issue, when it`s really the PCV hose... Access to that hose can be dowright difficult, and easier when combined with replacing intake gasket - I`d mention this possibility as a common issue on our cars to the mechanic in case his diagnostics got fooled by a hidden leaking hose under the manifold gasket he suspects is the cause....
 

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never thought of that one LOL, now this 90 elbow collapsing on itself does this hold true to a brand new car also?
Stupid me [?|] I didn't even look to see what year car you had. Our PCV hose is in a more difficult place to get to, and yes you nearly have to remove the intake manifold to work under there. Look under the car above the oil filter housing. You'll see a black box on the side of the block with a hose about 6" long running out of it to the intake manifold with 2 bends in it. At the black box is the PCV itself, and the hose goes to the intake manifold. One way to see if your PCV is either stuck or has a hole in it or something without having to remove and re-install one- is to simply unplug it from the intake manifold, then cap off the intake manifold- venting the PCV to the atmosphere. If your problem disappears- you'll want to replace the hose and valve at some point. If it doesn't, then plug it back up- it's not your problem.

Man, there is not a lot of vacuum on these engines as far as lines. I physically trace stuff. A vacuum schematic is on the VECI sticker under the hood. Brake booster, evap purge line, PCV, and that's about it as far as memory serves. All those except the PCV are easy to get to- on top of the engine or easily located in the engine compartment. Wait for a data log if you wish, but you should be able to figure this one out the old fashioned way- if you're on the right track at all by assuming it's a vacuum leak on the intake manifold side of the throttle plate.

Problems on the air intake side can cause some of the same issues- lean codes, etc. I'm having a particular crazy time with my K&N CAI- it sucks too much air. I think I know how to "fix" that, but I just haven't had the time (wife, kid, work, FF- where's me time?) recently. I know my O2 sensor is due for replacement, but it ran without lean codes before- so I want to try to get it back to that point before swapping. In your case with the FS Werks- have you cleaned it recently? Did you oil it? Did you clean the MAF weekly for a few weeks? That oil on the filter will cause lean codes for a while depending on how much you drive.
 

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Discussion Starter #9
yesh I cleaned the tb plate it seemed like the pedal was really easy to move after I did now it's back to normal and I'm still having the same issue. Since I'm on a fswerks intake and the filter that hasnt been cleaned yet could that be my issue..also remember the vac line or at least I think it's a vac line underneath the elbow right after the rubber hose coupler on the fswerks intake is that vacuum line? I have no codes or anything like that.
 

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Discussion Starter #13
And hey alex when I cleaned the t/b I did take out the maf too it wasn't to dirty and cleaned it with a rag but that's it I didnt mess with the filter should I switch to an aem dry flo? Has you know the filter is an itg foam element it looks clean to me the I/D of the itg is 3 inches right? just wondering because I might throw on a aem or something...
 
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