Vacuum leak?

[Kencart]

Hello,
I have a rather loud hissing (vacuum leak?) at idle that I cannot figure out on my 92 3.0 VZE. Almost sounds like it’s coming from the refrigerant lines but it occurs with the AC off (as well as on). It goes away at with the engine rev’d up but comes back instantly when returning to idle. None of the lines seem to be leaking. I thought maybe the pair valve but if I pull the lines off the VSV and put them together, manually engaging it, I hear the valve open and no change to the hiss.
Additionally, I have been having trouble setting my idle (but I’m assuming this supposed leak is the problem).
Any suggestions?
Thanks!

 

[Hyde802]

spray a little starting fluid where the hiss is coming from, if it revs up, inspect that area more.

 

[Kencart]

Tried that. No effect.

 

[RonJR]

Get a 3 foot length of garden hose or fuel hose and use it as a stethoscope - one end to your ear and the other probing various areas. You'll hear the leak loud and clear when you get close.
Be VERY careful around the fan belt while doing this!

 

[Kencart]

Well that was enlightening. I found air sucking in through the filter on the fuel pressure VSV. I looked at the diagram to make sure everything was hooked up right and apparently the PO Had put the egr and fp VSVs together backwards? The filter was where the vacuum line goes, vacuum line I think on the port that goes to the valve etc. I haven’t drawn it out, maybe it works the same way in that configuration but the filter is no longer sucking air.
That said, I still have a vacuum leak somewhere. Seems to be under the intake plenum. Injector? Plenum gasket? Anything else under there that could cause it? I notice adjusting the idle does increase/decrease the sound of the leak if that means anything.
Also, I noticed a broken bolt on the valve cover. I do hear the hiss slightly in that area but if I pull the hose from the other valve to the TB and plug the holes there is no change to the sound so that cannot be the issue correct?
Thanks!

 

[4RunnerNorway]

spray a little starting fluid where the hiss is coming from, if it revs up, inspect that area more.

I second this

 

[4x4withcheese]

Hello, I’m having a similar issue with my 95 v6 4runner - I don’t think it’s a vacuum leak, I’m wondering if it could be the Idle Air Control valve. The engine idles at 1500-2000 RPMs most of the time lately, whereas it used to idle at 1100-1200. I replaced the spark plugs and wires and found leak spots in the air intake hose so replaced that as well. After those replacements it still idles high yet the RPMs lower to normal levels when I go to accelerate after idling, which makes me think it’s specific to the idle control. Has anyone experienced this before or have advice?