1995 Tahoe 5.7 Vacuum Line Issue

[2doorfeller]

I recently bought a 1995 2 door Tahoe 4WD with the original 5.7 TBI with 278XXX miles. I have a vacuum line that originates behind the TBI from a metal fitting threaded into the top of the manifold. The line is then draped over the drivers side valve cover and is not connected to anything on the other end. The open end of the line draped over the valve cover is pulling a pretty strong suction, and makes the engine idle rough and run rough as I am slowing to a stop. at idle when I cap the open end with my finger, it does slightly smooth out the idle. My question is does anyone know where this line is supposed to connect to, or is it supposed to pull atmospheric air into the back of the manifold. Any help would be greatly appreciated.

 

[2doorfeller]

Here are a few images of the vacuum line in question.

 

[OR VietVet]

Brake booster? PCV valve? Get a vacuum schematic for the engine and look. Got to be able to google and find.

 

[2doorfeller]

I have Google several vacuum line schematics, and they do not show that line on them, or I am missing it on the schematics. The only place I have seen that the line will reach to that has a fitting it fits on is the ac evaporator, and it doesn't run well all at if I hook it up there. I am at a loss.

 

[Gzes]

I'll look at mine in a while and let you know

 

[2doorfeller]

Thanks Gzes, that would be great.

 

[SunlitComet]

a manifold vacuum line is likely the brake booster. might have been taken off because of a leaking booster. is your booster hooked up.

 

[ezdaar]

Booster is hooked up to that hard metal line that runs down the top of the manifold next to driver side valve cover.

That looks like the evap control hose,mand it has rotten in half.
Look down behind driver side headlight, infront of the wheel well for a black canister. It's about the size of a 2 liter soda bottle.

Look for another hose not hooked up to anything.

But definatly for now plug that hose up with a bolt that fits tight ot go to autozone and get a vacume port cap set. Then remove the hose and cap that fitting.

 

[SunlitComet]

looking over the hose routing again you appear to have mis-routed hoses in several places. pic from the service manual. you should also have this as a label under the hood which may feature more items on it.

 

[The_Nali]

Those two pipes running along the top of the valve covers are the secondary AIR injectors for the smog pump. The headers that you have on are not the correct model, the should have one flange each at the top where they eould connect into the exhaust manifold and run towards the distributor where the will then join at Y fitting and turn into rubber hose that connects into the secondary air injection pump. Its basically clutter, because it is only used 9 seconds average after you fire up the engine to cool off the cats.