On my cousin's 3.1L, he has a single blade throttle body. I don't know if that's what all MPFI vehicles came with or what, but on the top of the throttle body there is a rubber fitting with 2 hoses going into it. Their rather small hoses. I noticed that there is a 3rd hole for a hose towards the passenger side, but it is blocked off. The throttle body has passages for it and all. I was just wandering what it does and what hose hooks up to it?

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

hmmm....the one in the center goes to the fuel pressure regulator so i think that is a vacuum line. i couldn't see where the other hose went but i assume it's a vacuum line also.

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Dan
100% stock 1990 RS 3.1L
and VERY slow

 

Is this 3rd hole you're describing rather large? Like, near a 1/2 inch big?

On my 2.8, there's a thick black plastic hose that runs backward, between the plenum (spider) and intake manifold. I think it's for the cold start injector (I forget).

Did your cousin ever have work done to that car? I think the cold start injector was dropped in later years.. he could have a 2.8 throttle body. And yeah all the multiport throttle bodies that I know of were the same- well, I guess except for this hole.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

 

Yea, umm, the hole is plugged though i was just curious as to what it did. Always eager to learn what things on an engine do... no matter its displacement or horsepower.

------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

Cool, I feel the same way! It's funny how the problems can all be solved the same way... I once worked on a friend's Mustang. She had the I-4 2.3l motor in there, and it was stalling and had no power. She said 5 other people looked at it and couldn't find anything wrong. I thought "wow, what the hell can I do then?" I pulled a plug wire off the distributor, intending to check the wire, and rust fell out of the boot! Everything "obvious" was wrong with that motor- apparently nobody else knew what to look for.

ANYway, I'll look at that tube on my motor tonight to see where it goes. I wonder if the tube was dropped on the later 3.1 motors- can anyone with a 3.1 verify this?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

 

It goes around in the TB, and that's about all i know, heh My L98 is stall from stop so i have my own little problems, just no time to look into as school tends to distract me...

------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

As to your car, it's not the mass air flow sensor, is it?

Anyway I think I realized what you were talking about- that third port you're describing on your cousin's car- is it in that rubber block with the other two thin vacuum lines? If so, I was describing the wrong part to you.

The part I mentioned is on the -extreme- passenger side of the throttle body, facing the rear. If you're talking about the third plugged hole in the rubber block, well, mine is also plugged. Maybe GM used that block on a few cars? I seem to recall that yanking the block out reveals only two vacuum holes going into the TB.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

 

Yep thats the rubber block. So no idear as to what the third hole does or what would go to it?


------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

It probably connects to the other two holes. I'd imagine GM had a couple different cars using that block, each with a couple different routes for the vacuum lines needed. Apparently it's not used for the f-body v6's.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

 

His TB i think does reveal a third hole, if i can i'll take a look tonight and maybe see if i can take a picture...

------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

I have the third hole also 2 tubes going in and one plugged up... on my moms 3.1 she has a 92 olds cutless supreme all 3 are being used but cant see were it goes to next time i work on it ill take a look its fun havin the same engine n both your cars.. Except hers is a bitch to work on gotta love FWD cars

 

lol, and i though 350c.i. covered in hoses and wires was hard to work on.

------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

that plug is a the idle stop screw it regulates the minimum idle speed of the engine its factory set they put that plug there to prevent tampering i have all the directions on how to adjust it if you want them

 

Two vacuum lines come out,one goes to the fuel regulator the second drops down by the throttle body where it "T's" into the line coming from (or going to) the EGR crap.The other end of this line goes to your fuel vapor canister(or somewhere in that area).Where this mess plugs into the throttle body is what creates the vacuum.The vacuum supplied for this line needs to come from somewhere. I don't know if the 3rd area of the plug you are talking about was ever used.But I will do my best to find out.

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[This message has been edited by Kevin S (edited October 14, 2000).]