tt9714

OK, can someone enlighten me as to the purpose of the vacuum line connection to the throttle body on the 951?

<a href="http://boards.rennlist.com/upload/throttle_body.jpg" target="_blank">THROTTLE BODY PICTURE</a>

I was just replacing my intake manifold, and I confirmed that a vacuum line goes from the bottom of the throttle body to the intake manifold (ties into same banjo bolt as KLR sensor line).

Since the hole for this line is on the upstream side of the throttle plate (i.e. on the intercooler side), this vacuum line would serve to equalize the pressure on both sides of the throttle plate.

Jax951

Refer to this thread, and all shall be revealed!!

<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=15&t=006666" target="_blank">CLICK HERE!!!</a>

It actually goes to the temperature valve - you mistraced your vacuum line.

special tool

I believe that signal goes to the temp. sensor which is right below/rear of the cycling valve. The red remaining port on the temp. sensor then goes to the gas recirc. valve in front of the fusebox.

tt9714

Thanks for the quick replies guys. Now that I think about it my car is set-up like the diagrams. The routing was kind of a blur from last night.

So now that we have established the connections, can someone describe the operation of the parts?

I'm assuming that the temperature valve opens when the engine coolant reaches operating temp. This will then allow a vacuum signal to go from the throttle body to the gas recirculation valve. If the gas recirc. valve receives a signal then it will allow gas vapors from the fuel tank to recirculate through the J-boot air intake (via a small vacuum hose). Does this sound close to being correct?

Jax951

WOW! That's an interesting theory. I've never been able to figure out how it works, but it sounds plausible! Mine was disconnected entirely (sliced in two). I didn't see any noticable improvements after reconnecting it either. Then again, I've only put about 10 miles on it since then...

Anyone else?

Danno

I think it allows fumes collected by the evaporative canister to be dumped back into the intake once the engine has warmed up.

bs

hmmm... i will have to refer to my bosch automotive handbook tonight to double check, but i think the evap purge cycle happens when the engine is *cold* to richen up the mixture a little. plus that would explain that weird sound that i always hear for a second or two about 10 seconds after starting the car.