exhuast manifold leak = low vaccum?

[janks85]

hey i posted yesterday about some problems but i might have found it, Can and exhuast manifold leak cause low vaccume at idle? cause i found a pretty decent leak im my exhuast manifold gasket that is pushing a decent amout of air out

thanks
chris

 

[WeaselHack]

An exhaust manifold leak shouldn't have any impact on your vac, an intake manifold leak on the other hand will! Have you performed a boost leak test? When was the last time you checked your compression? And exactly how low is your vac? -10 in Hg?

 

[janks85]

yes compression is good its about 170 across the board... vaccum sits at about -12 at steady idle, i know a intake leak would cause vaccum but im not understanding why my vaccum sits low..sumtimes it goes to about -14 when its warmed up, could it be that my vaccum sits lower because of vaccum lines being deleted? cause i have no boost leaks and compression is good thats why im so confused

thanks
chris

 

[WeaselHack]

Okay...If compression is good and you are SURE you have no boost leaks I would check your timing next. Make sure the cam sprockets line up correctly and to take it a step further, check the timing advance at the crank with timing light. Just out of curiosity, is you PCV and breather still connected or have they been eliminated?

 

[janks85]

no he the kid before me put a little breather over the one to the CAI and block the intake nipple and the one to the manifold is still their but was never replaced...maybe i should start their? is their a part number for that or is it universal, i appreciate the help very much

 

[IslandTSI]

I have had a pretty significant manifold leak for a while now and my vacume has been rock steady at 19 inches at idle. It shouldent effect your vac

 

[WeaselHack]

Well...There is some debate about running a breather instead of having it connected to the intake but I don't think this is causing your issues. But just for kicks you might want to reconnect it. What about the timing? Have you checked that? Also, how much PSI were you running when you boost leaked and how long did it hold pressure?

 

[janks85]

i just found a leak on my throttle body, on the throttle shaft im guessing the #7 oring where the cable connects.. its starts to leak at like 2 psi, so im guessing that might be my culprate right their...Does that sound like it could be

 

[WeaselHack]

Absolutely! I have a leak in the exact same spot (TB Shaft Seals). I bought the replacement seals, attempted to remove the screws that hold the TB plate to the shaft and one of the stripped. So I gave up and live with the leak for now. It's a very simple job if you want to do the rebuild and if I recall correctly there is even a vfaq on it. In my case I think i'm just going to pay this guy: http://www.throttlebodys.com/ to rebuild mine and bore it out to 63mm and block off the FIAV while hes at it.

Just out of curiosity, does your idle surge?

 

[janks85]

yes it does, it will idle steady while my car sits(after i first start it) then when i start driving, very light i hit or stop i make my idle is all wacky will drop very low then spring up and if im sitting long enough it will even out but only until i start going and stop again

 

[nightspeed87]

my injector seals leak and causes a boost leak check there.
Do the 3000gt tbs work on 4g63? And would it be good to use if it does.