No announcement yet.

Rough running-suddenly

  • Filter
  • Time
  • Show
Clear All
new posts

  • Rough running-suddenly

    My '59 went from running great to running really rough and stalling overnight. I think it's probably a vacuum line. There's a sucking sound, and she's not losing any fluids. Am I probably right to change all the vacuum lines, and is there something else it might be?

    Thanks in advance for the help,

  • #2
    I would plug the vacuum lines going to the brake booster and fuel pump and see if it helps before replacing everything. It could be dirt in the carburetor as well as a number of ignition related items. A few things to check are the vacuum advance in the distributor and the coil resistor.
    John Pizzi - Squarebirds Administrator

    Thunderbird Registry #36223 856-779-9695


    • #3
      Jim, vacuum line is readily available in auto parts stores, everywhere. If you car's vac lines are hard and brittle, by all means change them. Bring a piece in to the store and tell them how many feet you need.

      Auto parts stores also have the little tees for windshield washer lines and vacuum lines. Over the years, polymers tend to bake out of the plastic, then they break all by themselves. Replace with nylon when possible.

      A broken vacuum line (anywhere) will cause your engine to run too lean, so fix the problem at your earliest convenience. If you cannot find the leak, start at the intake manifold, plug the vacuum hose with a bolt, and continue downstream until you get to the problem.

      One of the 'trickiest' leaks to find is in power brake boosters. When they 'let go', it's usually a large vacuum leak. Good luck. - Dave
      My latest project:
      CLICK HERE to see my custom hydraulic roller 390 FE build.

      "We've got to pause and ask ourselves: How much clean air do we need?"
      --Lee Iacocca


      • #4
        Take a look at your choke, it may be stuck closed. Good luck, Bob C


        • #5
          Suppose he cuts into a vaccum line, puts a T in, and runs a line to a vaccum gauge.

          a) what should normal behavior show up as?

          b) what would indicate a leak?

          One could easily run the temporary line inside the car and watch it while driving.

          1958 Hardtop
          #8452 TBird Registry



          • #6
            Good question, John

            The best answer I can give is, go to this web site where they have an animated display of gauges (and how they should read with different faults):
            CLICK HERE

            Eighteen inches of mercury is healthy vacuum. Yes, some get over twenty, but power boosters, etc., depend on eighteen as a 'standard'.

            I like the idea of watching a vacuum gauge as you drive because you can see what happens at the light, when your trans shifts, when you stop, etc. - Dave
            My latest project:
            CLICK HERE to see my custom hydraulic roller 390 FE build.

            "We've got to pause and ask ourselves: How much clean air do we need?"
            --Lee Iacocca


            • #7
              18 inches and steady vacuum is what you are looking for. Fluctuations can be fuel, ignition or valve issues. I would change out the fuel filter and see if that improves it. My problems with engine idle quality have been almost always fuel related and/or dirt in the carbeurator.

              CLICK HERE for Jim's web site


              • #8
                h ross perot

                Ross tried to warn us about that giant sucking sound.
                hold hand over carb air inlet while idling . close it off alittle at a time
                if idle speeds up you got a leak or weak idle ciruit.
                put in a lunati 60001 cam and my idle for power brake is way up
                and it purrrrs.