pics of what i can not figure out for plastic/small hoses are down in bottom of thread please help! alright i know how the vaccume diagram goes for a 1991 350 i have the emission hose routing diagram for the engine, but what i can not seem to find anywhere, not even in my gm service manual(or im just looking in the wrong places)but anyways i can not find any diagrams for those hard plastic hoses and any other hoses that go along with it, i get a constant hissing when i have my temp control on heat inside the car and i know its because of a few hoses are not in the right spots or are not even hooked up hopefully someone can help me, if i have to ill get pics up tomorrow im in the middle of taking out my old harness and putting a clean one in so i figured while i have everything out of the way get it done!

Sounds like the one way valve is either not hooked up right or not there. I had that issue when I put my car together.. had it in the wrong place.

I'm in Manchester all the time.. don't think I've seen your car around though.

what do you mean by the one way valve?

cause right now it does not look anything like my picture, im out past andover on weekends sometimes(nights), the car is blue, primer grey, silver, red, and has an iroc hood now(all primer grey)
link to the bodywork thread i started(has updated pics)

http://www.thirdgen.org/techboard/bo...ork-paint.html (starting body work for paint)

there should be 3 ports comming off the back of the plenum, one for the MAP sensor, one for fuel pressure regulator, and one for th HVAC and cruise. The last one has a T in it to split to the cruise control and the other way to the HVAC line.. I forget how it's supposed to be connected up exactly off the top of my head, but somewhere is a little plastic cone like housing inline. I'd have to look at my car to see how it is set up.
Also it could just be a loose or cracked line at the back of your HVAC control panel.

doubt its cracked at the back of my hvac control, only because it worked perfectly fine before when i had the v6 in! well im goin out now to start workin on the car again, praying it doesnt snow like the weather says
ill get some pics if i cant figure it out

alright here are a couple pics of the few hoses i can not figure out

hard to tell since its all bunched up...

but from what i can see,the very first pic,is for your HVAC,the second pic is the heater diverter valve

you should plug the vaccum line from the first pic,into the valve in the second pic...{it controls flow of hot water for the heater core}

third pic is the EGR solenoid. for this,on my iroc,the shorter line goes to the EGR,the longer line goes up to the driverside port underneath the throttle body.

the fourth pic,just shows all the vaccum lines,trace them all out and find out where they lead too,and i can help more,if you need pics of how its suppose to look,let me know and ill run out and grab some for you.

wow in the fourth pic looks like someone has a hose problem and made their own design to bypass a few things to make the car driveable or tolerable to just drive but definately not stock. I'm guessing your not teh first owner? Is that how you boguht the car or did you start taking thigns apart and forget whre they went?

My heater diverter valve has hard emission tubing to it. Could this be a problem and should i unhook it?

Ok I forgot about the heater divert valve, I hate those friggin things so I got rid of all that.
This is a MAF setup? I was thinking SD from it being a 91.. but that looks like the MAF plenum.
Anyway i agree with what iroc88lb9 said.

I would guess A is for the EGR
and B and C connect to each other with B being the other end that iroc88lb9 said to connect to the diverter valve.

D seems pointless unless it's a speed density conversion setup and that could be for the MAP sensor.

BUT, that's just a guess since I can't really see how the lines run. Would be a lot easier to figure out in person.


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No they have a hard plastic line originally from looking at an old pic of my car.

well,looking more closely at this...

without being there,its hard to judge. but in the larger pic jay just posted,if i had to make an educated desc,based on that pic....and his letter abreviations..heres my diagnosis

line A looks to be routed,and long enough to be for the EGR,id check and see if that routes to the front driver side under the TB,thats my guess.

line B ,looks to be the line that goes to the actual EGR itself,which should also be plugged into the egr solenoid switch.

line C looks to be Hvac,since it clearly looks like it routes into the firewall

line D that one im not sure about,my IROC doesnt have A/C.


if i were you,i would rip ALL of that crap out,and just reroute,re vaccum wire the car based on factory diagrams,heres why,i bet all the plastic lines crack way easy,and the rubber lines need to be replaced anyways.

if you want pics of the routing on my car,let me know and ill take detailed pics.

well i have it all straightend out, biglou talked me through it and we got exactly where they all go, thanks for everyones input and help!