Vacuum schematics 1991 Suburban Help please

Discussion in 'General Chevy & GM Tech Questions' started by 91SUBURBEAST, Jul 11, 2011.


    91SUBURBEAST Member

    Does anyone have the vacuum hose schematics for a 5.7 throttle body 1991 motor. The previous owner made a mess of my vacuum hoses and I need to fix them. Any help would be greatly appreciated. Thanks in advance.
  2. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    There should be a sticker on the front radiator core support the describes the emissions setup with vacuum hoses. I'll try to get a pic of mine later tonight. For the other vacuum hoses, a Haynes or Chilton manual might have it.

    91SUBURBEAST Member

    Thanks I appreciate it. Haynes definitely doesn't have it but a chilton might. Any help would be appreciated.
  4. MightyMax

    MightyMax Rockstar 100 Posts

    If it would help, I could snap some pictures of my truck and post them.

    It is a '91 350
    It has had an Eddlebrock Intake put on it, but still stock TBI

    Let me know and I will post it.

    91SUBURBEAST Member

    That would be allot better than where I'm at right now...can you please post pics of your truck.
  6. MightyMax

    MightyMax Rockstar 100 Posts

    This is looking at the TBI from the front.
    There are 3 hoses, the one on the left goes over to a sensor, I can't recall its name
    The one in the middle goes to the valve cover, the one on the right w/ the black plastic wrap around it, is coming from the canister behind the headlights.
    That line inbetween the left and middle hoses, is a bundle of wires for powering the injectors.



    This picture is from the back, there are two fuel lines and the hose in between them goes over to the MAP sensor.


    This is from the back of the TBI also, just from the driver's side of it.

    That is the MAP sensor I believe that the hose on the back goes into.

    Hope this helps you.
    Let me know if something else is needed.

    91SUBURBEAST Member

    Thank you! This is definitely not how mine are currently routed. Now I can fix them and diagnose any other problems from there. Thanks again!
  8. MightyMax

    MightyMax Rockstar 100 Posts

    Welcome, let me know if you need something else.

    I will use a better camera then....that was with my phone, which isn't the best. :(

    91SUBURBEAST Member

    Lol...I know when I blew them up they were all digitized. Thanks still the descriptions are really helping.

    ---------- Post added at 09:22 AM ---------- Previous post was at 09:09 AM ----------

    Ok question...on the map sensor there are two hoses. Which one goes to the throttle body and which one goes to the vacuum canister on the intake? Also there is another vacuum line at the rear of the intake manifold where does that connect to? There is also one more on the firewall itself going to the round canister by the firewall where does that attach? Thanks for all your help.

    ---------- Post added at 09:27 AM ---------- Previous post was at 09:22 AM ----------

    I'm sorry it isn't the map sensor that those other hoses go to its the rear if the sensor the neither of us know the name of lol.
  10. MightyMax

    MightyMax Rockstar 100 Posts

    Ok, I think that sensor is the EGR Control Solenoid

    The one you mentioned on the firewall, is that located on the driver side of the firewall??
    Big round thing??

    If so that is the brake booster, and his vaccuum is attached to the front of the intake
    His hose is located beneath the TBI, and actually goes into the intake on the front side, next to the driver side valve cover.
    If you look at picture two above, that is the line that is located right above the word "PERFORMER" stamped into the intake.

    ---------- Post added at 01:13 PM ---------- Previous post was at 12:59 PM ----------

    That EGR Solenoid is attached to the under side of the Electronic Spark Control Module.

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