Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Vacuum Leaks/Running rough

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1990SilveradoK5, Apr 25, 2001.

  1. 1990SilveradoK5

    1990SilveradoK5 1/2 ton status

    Joined:
    Jan 2, 2001
    Posts:
    185
    Likes Received:
    0
    Location:
    Napoleon, OH
    What is the easiest way to find a vacuum leak.

    My 90K5 w/ 350 was running rough this morning on the way towork, as it does about once a month. Engine light came on and when I got to work popped the hood and heard an air leak type noise cycling on and off on the drivers side of the engine bay. It did not sound like an exhaust leak but a slower cycle somewhat like a compressor. (1-3 seconds on then off)





    Gone Large and Loving It.
    Keith
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Get a can of carb cleaner, put on that little tube, and start spraying around the leak. When your idle changes, you've found the leak because it sucked up the cleaner. Write back to where the leak is and we'll fix ya up. I doubt its your compressor because it is effecting how the motor runs.

    [​IMG]
     
  3. jimmyjack

    jimmyjack 1/2 ton status

    Joined:
    May 11, 2000
    Posts:
    2,290
    Likes Received:
    0
    Location:
    Tucson Az
    Spray the base of the carb and along the sides of your intake manifold and your vac hoses.Be careful spraying the carb cleaner near the distributor. Its explosive. I sprayed some exposed wires on my dist. and it blew up in my face.

    Basically the carb cleaner will displace the oxygen and your motor will pick up briefly til it burns off the carb cleaner. Some will spray into the carb opening so just use little squirts if you can. Sometimes it helps to remove the fan belts so theres no air circulating. Just don't run the motor for a long time.

    "My blazer may be slow, but it goes faster at higher speeds"

    Jim
     
  4. 1990SilveradoK5

    1990SilveradoK5 1/2 ton status

    Joined:
    Jan 2, 2001
    Posts:
    185
    Likes Received:
    0
    Location:
    Napoleon, OH
    Well, it ran fine on the way home last night, even at idle it was smooth. I still tried the carb cleaner trick, however I did not notice anything change while spraying it.

    I do have TBI would that make a difference in troubleshooting the rough running?



    Gone Large and Loving It.
    Keith
     
  5. lowlevell

    lowlevell 1/2 ton status

    Joined:
    Jun 27, 2000
    Posts:
    343
    Likes Received:
    0
    Location:
    Central Ohio, USA
    Since your engine light came on, you can run a diagnosis on it. Very easy to do. If you dont already have one, pick up the book to your truck from the library. It will tell you how to do this. I will not say how to do it because i cannot remember off the top of my head which pins to "jump".

    Also, on my 89 350 TBI, the vacuum lines are plastic and not the old rubber line type. A few of my rubber ends(at the ends of the plastic tubes) were dry rotted at the carb (throttle body). Their isnt very many lines to check (as compaired to the pre 87's), so just give them a quick check and look for loose connections, cracks, or even burn marks. Later.....

    One From None
     

Share This Page