Boost/Vaccum leak at intake mani

[slick06emp]

ok so ive been working on some boost leaks that i have and found quite a few around the throttle body. my question would be....is air supposed to be able to get by the tps sensor? and the vac lines on the back side of the intake manifold i have a few ports that are just open and not blocked off. could that be another big cause of my studdering at boost?? any help would be great.

 

[habitatguy187]

A picture would really help here.

 

[Pirrofab]

Studdering under boost can also be caused by a failing ignition system. (plugs/wires/coils)

However, boost leaks are major contributor. The air leaking out from behind the tps sensor is indication of the throttle body seals. On a 4g63 turbo the 2 lower vacuum steel lines that run under the intake are not used on both sides so they aren't the issue. Atleast they weren't used on my 92 when I was replacing my intake gasket. Another common issue for boost leaks is the injector o-ring seals. If you remove the throttle body elbow make sure you replace both gaskets on the throttle body because the throttle body is sandwiched between the elbow and intake manifold. Also. If you remove the biss screw make sure you either replace the o-ring for it or wrap the biss with teflon tape and then reset the idle. There are a few members on here that do throttle body rebuilding with great results. I don't remember the ones name but hopefully he will chime in on this. I believe he lives in Pa but I'm not sure where.

 

[snowborder714]

I'm probably the rebuilder you're thinking of


If air is leaking from the TPS, then your shaft seals are leaking and the throttle body needs rebuilt.

If you have open nipples on the back of the intake manifold, cap them off with vacuum caps and put zip ties around them to ensure they stay on.

 

[slick06emp]

as ive been working on it today i capped all the vaccum lines that arent used off. i resealed the throttle body on both sides as well. im working on gettin everything else hooked back up to give it a whirl. im hoping i wont need to rebuild my throttle body....how much would that cost??? plugs wires and coil pack have already been eliminated as possiblities. thanks for teh suggestions guys!!! its making my day a little easier

 

[the_mork]

About $10 and an hour of your time.

Really rebuilding the TB is more expensive but also usually unnecessary. New shaft seals are generally all you need.

An impact driver is a help too in getting the throttle plate screws out and they cost about $6 at harbor freight.

 

[Pirrofab]

I'm probably the rebuilder you're thinking of


If air is leaking from the TPS, then your shaft seals are leaking and the throttle body needs rebuilt.



If you have open nipples on the back of the intake manifold, cap them off with vacuum caps and put zip ties around them to ensure they stay on.

Yesk, your the one I was thinking of. Haven't had to rebuild mine yet since there only a very slight leak but it seems that everyone else is happy with your results so when mine do need rebuilt. there going to you if I can't figure it out.

 

[GSTtex]

Not to hi-jack the thread, but I too have a boost leak, coming from an unknown source near the intake manifold. It is a constant hissing sound within the engine bay and is continuously getting worse.

So far I have purchased carb cleaner to spray the intake manifold with, knowing that if the RPM's shoot up, it is either a cracked intake manifold or a broken intake manifold gasket.

Now you guys are talking about vaccum lines that run underneath the intake manifold, I presume? I have recently changed my injectors to RC 550's, but the boost leak was there before I replaced the injectors..

Any help? Before I go out and rip the intake mani off..

 

[the_mork]

There are no vacuum lines under the manifold.

Spend $5 to make this IC Pipe Tester and then use a spray bottle with soapy water to find the source of the leak.

 

[Calan]

There are no vacuum lines under the manifold.

Not sure about the 2g, but on a 1g the emission vacuum lines go under the rear of the manifold, and connect to each other via 4 tubes welded to the manifold stay. If a line is off or broken here, it's a bit hard to find but can sound like a leak under or behind the manifold.

 

[the_mork]

AFAIK there are no lines under the manifold on a 2g. Our charcoal canisters on a 2gb are near the battery and IIRC on a 2ga they are toward the front of the car.

 

[slick06emp]

well i got most of my problem resolved. the throttle body has new shaft seals (the old ones had like no rubber on them anymore) and new gaskets, i had to use some gasket maker on the elbow side. apparently my elbow is very straight and wouldnt seal so i put a nice bead on it and she sealed right up. now i move on to buying some injector seals!!!!!! this is where the rest of my boost leak is at.

on a good note while i had it all torn apart i shaved my intake manifold and valve cover and polished them.....i can see my face