What is this? its brass and sits on the back top of a 1995 3.0 4Runner engine

 

That, if you mean the brass bolt looking thingy with 2 vacuum connectors, is a temperature controlled vacuum switching valve. I'm not sure exactly which one. Check the vacuum diagram on the underside of the hood, upper left corner when the hood's open, for a VSV that matches it. I suspect it may be the one that controls the FPR when the engine is started hot.

Be careful if you go to remove it. You'll need to drain some coolant out, or it will come out the hole. Also, those plastic vacuum connectors get brittle with age, and can break off easily.

If you want to test it, leave it in, and attach a short length of vacuum tubing that will reach your mouth, or a vacuum pump/gauge set. See if the capability to blow air through it changes when it's heated up. Or take it out, dip the end in pot of water, again with the vacuum lines on it, And bring the heat in the water up, seeing if the ability to blow air through it changes.

Does that help at all?
Pat☺

 

yes! thankyou! I dont know what FPR means..lol

 

FPR means Fuel Pressure Regulator

 

So if that thing's unplugged like that it would mess up the way the engine runs?

 

Not necessarily.
It tthere to increase the fuel pressure in the fuel rails when the engine is in a heat soak condition. You notice that if you drive around until the engine is good and warmed up, the oil is nice and hot, etc, then shut it off, and then go to start it up a few minutes, like 10-15, the temperature gauge is way up, but comes down to normal quickly. That rise in temp is the "heat soak".
When that happens, it can cause bubbles in the fuel rails, as the fuel vaporizes due to heat. Well, when that happens, it's hard to start, hesitates, and so forth. Raising the pressure in th fuel rails helps prevent that. The higher the pressure, the higher temp is needed to cause the fuel to vaporize in the fuel rails.

Does that explain it a bit? Is it now clear as mud?
Pat☺

 

no i understand all of it..lol

 

Oh good!
I know I tend to get a bit overly verbose (big words, huh?) at times, so If I do, just tell me to shut the hedoublehockeysticks up

Glad I could help, though. Really. If you're not extremely careful, you can learn something new every day

Like I said, be careful, those plastic parts get very brittle, so if you go to mess with it, be ready to order a new one. If you HAVE to drive it after breaking them, just plug the two vacuum lines. I use a small screw to do that, but anything that fits, works. Otherwise, just leave everything alone, and let it cool down before you go to start it again. No heat, no heat soak, yes?

Have fun!
Pat☺

 

Oh I'm learning all right. I learned also to cut a hole under the seat of this thing in order to change the fuel pump LOL

 

Thermal Vacuum Valve (TVV) or Bi-metallic Vacuum Switching Valve (BVSV).

It connects the output of the Evap Canister to the throttle body. When the engine is warm enough, engine vacuum sucks the vapors stored in the Evap Canister into the intake.

(It has nothing to do with the FPR or fuel pressure at all.)

So where are your hoses? It could be that someone connected the output of the Evap Canister directly to the throttle body, bypassing the TVV. In that case, the engine will run rough for a while if there are vapors in the canister.

 

I have the evap canister hooks to the little metal tube just above that. Do you know the routing for that?

 

Ok, It's BMSV. I did say I was guessing as to it's purpose I guessed wrong, as is often the case, that's all.

Sorry about that...
Pat☺

 

"that"? The hose from the Evap goes direct to the TVV. The hose from the TVV continues to the left (left as you're sitting in the driver's seat) to a metal tube. The metal tube continues, to a hose to the throttle body.

Your vacuum sticker should look something like this:




Sounds like your TVV has been bypassed. As 2ToyGuy mentioned, the "usual" problem with the TVV is that the plastic body becomes very brittle, and the ports break off. Be careful. Also, it's just a valve, so the order of the ports doesn't matter.

 

is that EGR modulator valve supposed to have a bunch of carbon buildup in it?..lol I took it apart and sprayed the filter out with brake cleaner and put it back together. It was bad.

 

Hmm. I guess that question kinda answers itself.

Here's the FSM page: http://web.archive.org/web/201204061...77exhaustg.pdf If you've already come this far, you should run the FSM tests to see where you are.

If you live where "smog checks" are required, the EGR system is vital in reducing NOx emissions. If you live someplace where people breathe the air, same thing.

Good luck!

 

Thanks scope103 for the FSM egr system tests should help narrowing down my high nox issue.