Is this supposed to be connected to something?

Is this supposed to be connected to something?

 

Should be a nipple on the back side of the intake tube right where the timing belt sticker is

 

This. Borrowed internet image with arrow added.

 

Thanks @shifty`

what’s that hose actually do?

 

Well, that silver thing it's attached to looks like it's related to the fuel rail, so I'm going to guess that's the fuel pressure regulator vent, making that rubber vacuum hose the fuel pressure regulator vent line.

What would happen if you left it unhooked? Not sure much of anything per se. It's a vent, and if I had to take a wild stab, I'd guess it's attached to the intake manifold tube so that any unspent fuel vapors would be pulled in w/intake air, and ultimately consumed again by the engine via that route.

Which actually, I believe, answers a question I had earlier about why that bulbous box is there. I'm going to take a wild stab that, similar to EVAP canisters, that bulbous protrusion on the intake tube probably has carbon in it to filter/capture fumes, and the vacuum of intake air helps pull them thru it.

I may be wrong on this, but given most EFI engines of the era have similar, I doubt Toyota is doing anything new here.

 

FYI It's not a vent.

It's the fuel pressure regulator air pressure source, that allows the regulator diaphragm to raise and lower fuel pressure with vacuum/boost in the intake, to maintain correct pressure at the injectors.

 

I think @shifty` nailed it. On my 2000 there are 3 hoses on the back of that cannister. The big one is a vent to the valve cover, one connects to the fuel rail dampener, and the third is connected to the evap cannister under the hood. The power steering power valve connects to the side.

 

I think we're actually both correct, it's doing both what you're saying and what I'm saying. But it's definitely a vent tee with vacuum hose, most FPR I've seen have them, and there is an emissions function of ensuring vapors aren't vented to atmosphere and an intake vacuum function acting on the spring in the FPR.

Where you look really reflects how you'll see it described.

For example, FSM.

​

K&N intake manual, note step 6.

​

 

Good to know

I was definitely throwing codes and running extremely rough a few months back when mine came off

 

If it's working as a vent... the regulator is bad and should be replaced.

 

I hear you, but I’d ask this: If there was no intention of vapors venting to the intake, why would Toyota bother attaching it specifically to a section of the intake with a carbon/charcoal filter? There are nearer sources, all downstream from the MAF, with no filtering.

 

Theoretically speaking, absence of vacuum on a FPR should result in higher fuel pressure, unless toyota has reversed the function of the FPR somehow. I'd expect rough idle to happen in a case of too-low fuel pressure. EDIT: And I can't see how the miniscule amount of added post-MAF air intake from a <2mm ID bib on the charcoal box would offset your air/fuel ratio enough to cause issues.

Just for S&G, next time I start the truck, I'm going to pop off the intake end of the hose and see what happens, and see how much vacuum is on the port at idle.

 

Following. Cause science.

 

learning something every day. I know on my 4runner it goes into the intake just after the maf

 

The box has no carbon/charcoal. It's just a resonator to quiet intake noise. Iirc.

The charcoal filter/trap is in the top side of the air box above the air filter on the later year trucks. This is to block residual fuel from the intake/injectors.

 

Regulator
https://www.rockauto.com/en/catalog...+&+air,fuel+injection+pressure+regulator,6124
Damper
https://www.rockauto.com/en/catalog...uel+&+air,fuel+injection+pressure+damper,6120
Spent some time on these two a long time ago... learning how they worked