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Engine bogs slightly when I let off the brake

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    #1

    Engine bogs slightly when I let off the brake

    Got a weird one. Anyone ever had this issue? I let off the brake at a light and the engine bogs for the half a second before I stab the skinny pedal. If I don't stab the pedal... it still only stumbles for about the same amount of time. I have no issues with actual use of the skinny pedal... so this one has me baffled.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Originally posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Originally posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.
    Tags: None
    #2
    Check valve on the brake booster, or a brake booster internal failure. Its probably causing a vacuum leak momentarily when the booster moves.
    -Steve

    2006 Audi A6 S-Line FWD ~132k miles, stock.
    1998 Mercury Grand Marquis LS HPP ~102k miles, slowly acquiring modifications.
    1997 Lincoln Town Car Cartier ~145k miles, Ported Plenum, Gutted Airbox, Mechanical Fan Delete, Contour E-fan Retrofit, Dual exhaust, Cats ran away, KYB Gas-A-Justs, P71 front sway bar, air ride reinstalled, Blinker Mod, Projector headlight retrofit, Caddy 4-note horn retrofit, Wood rim steering wheel, rustbelt diet plan..
    1996 Mercury Grand Marquis GS 117,485mi. R.I.P. 7/14/12

    Comment

      #3
      Originally posted by BigMerc96 View Post
      Its probably causing a vacuum leak momentarily when the booster moves.
      That would be my guess.
      2020 F250 - 7.3 4x4 CCSB STX 3.55's - BAKFlip MX4
      2005 Grand Marquis GS - Marauder sway bars, Marauder exhaust, KYB's
      2003 Marauder - Trilogy # 8, JLT, kooks, 2.5" exhaust, 4.10's/31 spline, widened rear's, metco's, addco's, ridetech's 415hp/381tq
      1987 Colony Park - 03+ frame swap, blown Gen II Coyote, 6R80, ridetechs, stainless works, absolute money pit. WIP

      Comment

        #4
        Also on board with vacuum issue, be it a booster issue or otherwise.

        Comment

          #5
          Sounds like my 89 sometimes. was going to try a new Ford check valve.
          -Nick M.
          Columbia, SC

          66 Squire, 89 Colony Park, 90 TC, 03 TC, 06 TC, 07 TC (2x)
          03 BMW 540iT, 07 Toyota Tundra SR5 Dbl Cab/5.7 2WD

          Comment

            #6
            Yeah I get the same on cold starts, and when I depress the brake pedal I hear a hiss until I let it go. Also, I hear a whistle (could e a vacuum leak in the brake booster). I agree
            "To Find yourself, you must first lose yourself"

            -1973 Volkswagen Bus Westy
            -1986 Honda Magna 700cc
            -1989 Lincoln Town car Signature Series
            -2011 Subaru Outback

            Comment

              #7
              I'll have to look into that. The booster had the mild leak while the brake rod is moving, pretty much since I got the car. I also have no issue with my brakes having boost... so I didn't even think it could be the check valve.

              Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
              rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
              Originally posted by gadget73
              ... and it should all work like magic and unicorns and stuff.
              Originally posted by dmccaig
              Overhead, some poor bastards are flying in airplanes.

              Comment

                #8
                Quick and dirty test, pinch off the vacuum line to the booster and see if the problem stops. I had leaks at the grommet where the check valve sits, and the check valve itself was bad. Wasn't causing me problems but it wouldn't hold vacuum in the booster as it should have.
                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

                  #9
                  Now the grommet may be an issue. It's pretty old. I don't think I've ever touched it in this car. I do know I get his from the booster when I stand on the brake at a stop light when I reach for something, so the booster may just have a weak seal itself. Definitely going to check it out when it warms up and not any sooner since it never dies and I don't have any braking issues.

                  Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                  rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
                  Originally posted by gadget73
                  ... and it should all work like magic and unicorns and stuff.
                  Originally posted by dmccaig
                  Overhead, some poor bastards are flying in airplanes.

                  Comment

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