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    #1

    Weak Cruise Control

    For the last six months, the cruise control on my car hasn't worked right. It will begin to hold the speed, but it doesn't do a very good job at it. If a hill comes up, the speed begins to drop and once the speed is 15mph below the target, the cruise control disengages.

    So far I know this:
    -Horn works
    -I swapped the entire cruise control servo + cable from a junkyard car and it did not solve the problem
    -The throttle cable may be sticky, but I'm not sure how to tell if it is for sure
    -Dump valve seems to be properly seated on the brake pedal
    -The symptoms started after a mechanic broke the TV cable while doing the lower intake gasket. Something else may have been broken in the process


    What do you guys think?

    1989 Lincoln Town Car Signature Series | 249k miles, current project car
    2018 BMW 430i xDrive M-Sport | 50k miles
    2018 Toyota Tacoma TRD Sport | 97k miles
    Tags: None
    #2
    see if the dump valve holds vacuum. It comes out under the hood next to the cruise servo. There is a line that goes from one side of the servo to the other, with a T in the middle of it. The line going into the firewall off that T is the dump valve. If it doesn't hold vacuum with a vac pump, that'll be it.

    Something else to check is the check valve in the vacuum feed to the servo itself. Find the vacuum line that feeds from the tree on the firewall to the servo. There is a tee and a check valve, or it might be a combo tee/check thing. Make sure that works like its supposed to, otherwise you'll lose vacuum under load. If the smog pump is gone, that will contribute somewhat to weak cruise under load but it shouldn't be too terrible if the vacuum system isn't leaky.
    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC grandpa spec white and cranberry

    1984 Lincoln Continental TurboDiesel - rolls coal

    Originally posted by phayzer5
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

    Comment

      #3
      At least yours works, my buttons do nothing.

      2011 Ford Ranger Sport 4.0 2wd - Magnaflow Axleback exhaust, K&N 63 Series CAI, DiabloSport 87 Octane tune, LEDs, 3000K LED projector fogs, 5000K Mini H1 projectors - Daily
      1967 Ford Galaxie 500 Sedan "C-Code" - 289 2bbl/Cruise-O-Matic - Money pit/project

      Comment

        #4
        It's probably the contacts on the slip ring. Mine seem to work, but it probably wouldn't be a bad idea to clean mine up anyways.

        1989 Lincoln Town Car Signature Series | 249k miles, current project car
        2018 BMW 430i xDrive M-Sport | 50k miles
        2018 Toyota Tacoma TRD Sport | 97k miles

        Comment

          #5
          I'll have to check it out gadget! What's the best way to check vacuum? I haven't done that before.

          1989 Lincoln Town Car Signature Series | 249k miles, current project car
          2018 BMW 430i xDrive M-Sport | 50k miles
          2018 Toyota Tacoma TRD Sport | 97k miles

          Comment

            #6
            use a vacuum pump to see if things hold. its a hand held thing you can get at an auto parts store for about 25 bucks. The check valves are fairly easy, you can just blow through those. It will pass one way but not t'other if its working right. There is an arrow to indicate which way things flow. Arrow should be pointing towards your vacuum source.
            86 Lincoln Town Car (Galactica).
            5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

            91 Lincoln Mark VII LSC grandpa spec white and cranberry

            1984 Lincoln Continental TurboDiesel - rolls coal

            Originally posted by phayzer5
            I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

            Comment

              #7
              I have developed this issue too. But if I ever so gently rest my foot on the gas, the cruise control goes back to where I set the speed at.

              Comment

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