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Idle issue with 99 Grand Marquis

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    #1

    Idle issue with 99 Grand Marquis

    Hey Guys,

    Been a long time since I posted on here. Been away for a while.

    My 99 Grand Marquis has started acting up a bit. It started once in a while about three months ago, but has got progressivly worse.

    When I start the car, and have it in Park or Neutral the engine runs smooth and fine. However, when I'm in drive, and idling the engine revs will fluctuate from normal to almost stalling. The car will also surge forward with the fluctuating revs (can feel the different pressure on the brake).

    I'm thinking that it may be a MAF sensor issue, but at almost $300, I don't want to needlessly replace mine if that's not the issue. However, that's really just a guess. Thoughts?

    Thanks.
    sigpic
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    #2
    check the contacts on the wire harness first just to make sure it's not corrosion being an ass.

    also, if you can get a hold of some MAF cleaner or contact cleaner and hose the MAF out, that may help too.

    another thing to check would be the canister purge solenoid (do newer cars have an evap system like the older ones?). If that's closed all the time, the idle may stumble when the computer is expecting fuel vapor to be added to the intake.

    of course, the usual... vacuum lines should be checked for cracks/leaks. The throttle body may also need to be cleaned up.

    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

      #3
      Iac????


      "Hope and dignity are two things NO ONE can take away from you - you have to relinquish them on your own" Miamibob

      "NEVER trade your passion for glory"!! Sal "the Bard" (Dear Old Dad!)

      "Cars are for driving - PERIOD! I DON'T TEXT, TWEET OR TWERK!!!!"

      Comment

        #4
        yeah... that could do it too... if you clean the throttle body... point the spray into the hole in the side of the throttle body that goes to the IAC. usually a nice bit of black gunk will drain out (carbon build up).

        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

          #5
          Try all of the above.
          If it continues, check your Crank Position Sensor (CPS). It's right about the AC Compressor. I had one start to go on me and it sucked ass. The car started bucking and would not idle or run for shit.
          Also, changing the air and fuel filters may help; depending on when they were last changed.
          Hope this helps.
          And please report your results!!!
          Thanks!!!

          -ryan s.
          08 Lincoln Navigator L - 233k
          03 Mercury Marauder- 63k
          97 Ford Crown Victoria HPP "Tank of Justice III" (TOJ3) - 194k -->578.9 miles on ONE tank of gas<--
          94 BMW 325i Convertible - 135k
          73 VW Super Beetle "Bunky" <----- Wifey's
          12 Mini Cooper S - 90k <---- Wifey's
          Originally posted by pantera77
          Well my buddy tells him he knows exactly who loves buying shitboxes.

          Comment

            #6
            Thanks for the responses guys. I cleaned the MAF and throttle body with no improvement. Will try the throttle body hole tomorrow (it's dark now), and then swap out the IAC valve, and if that doesn't work, then try the crank position sensor. Will keep you posted.
            sigpic

            Comment

              #7
              No chance that the air intake pipe between the MAF and throttle body is cracked, or any of the tubes coming off that pipe are unhooked, cracked, or loose is there ? It kinda sounds like a vacuum leak but I dont know the modular motor of doom all that well.
              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

                #8
                Check for vacume leaks since you said its at higher RPM's

                Comment

                  #9
                  I took the throttle body apart and cleaned the intake hole for the IAC. Seems to have sorted out the issue, and she runs smooth as ever now. Thanks again for all the tips.
                  sigpic

                  Comment

                    #10
                    These symptoms are usually an IAC on newer mod motors, its not quite old enough yet for vacuum lines to crack on their own. If it returns, pop off the IAC(two 8mm bolts on the back of the plenum) and give it a thorough cleaning. If that still doesn't do it, a new IAC for a '99 is about $50.
                    -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

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