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99 MGM spark knock at high throttle

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    99 MGM spark knock at high throttle

    Hi everyone, it's been a while since I've been on.
    The search feature didn't net any results after a half hour of reading.
    I have a 99 Mercury Grand Marquis Presidential with 77,000 miles.
    I'm experiencing some serious spark knock above half throttle in lower gears and at lower throttle levels in higher gears.
    No check engine light.
    I thought I would check the base timing, but the tag under the hood said timing wasn't adjustable.
    My number one suspect is a vacuum leak.
    Any "typical" problems or areas that I should be looking for, or am I barking up the wrong tree entirely?
    Any advice is most definitely appreciated!
    Thanks in advance!

    Rob

    #2
    Tried switching gas stations?

    How many miles on the spark plugs? I forget if the mileage for those is 60K or 100. I run platinums to 60k.

    Clean the MAF with the appropriate cleaner.

    Otherwise I'd suspect the EGR but that might throw a code.

    My 95 Ranger pinged but not after replacing the PCM and an updated flash from the dealer. My 00 F350 6.8 is very sensitive to gas brand, sometimes station to station same brand. It's not terrible, so I just let it go until about 1/2 tank, and fill up somewhere else and it's fine (87 octane).
    1990 Country Squire - weekend cruiser, next project
    1988 Crown Vic LTD Wagon - waiting in the wings

    GMN Box Panther History
    Box Panther Horsepower and Torque Ratings
    Box Panther Production Numbers

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      #3
      when was the last time the fuel filter was replaced? If its original, its way overdue. Running lean will make it ping badly.
      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


        #4
        Also check vacuum lines. Unmetered air getting in can be bad too. Also, try cleaning the MAF sensor with MAF cleaner or contact cleaner. Any other stuff may damage it. Also, no touchy the little wires... just hose them.

        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
          Well thank you all!
          I'm not a betting man, but I'd put $20 on EVERYTHING being factory parts and the whole car being on the deferred maintenance program.
          Although I do know that my grandmother did have the oil changed every 3,000 miles in the 13 years she owned it, can't vouch for the original owner, but one would assume that they would change the oil regularly on a vehicle they bought brand new.
          I'll pick up a new set of plugs, a fuel filter, and and air filter to start with.
          I plan on checking for vacuum leaks and cracked/broken hoses.
          I'll get some contact cleaner as well.
          Thanks again, I have a place to start from now!

          Comment


            #6
            In the many years driving Crown Vics. Every one I have used at work or owned did not run well on anything less than mid grade gas. At work they only had 89 octane. I always put 90-91 octane in mine. I would change the Fuel filter with a high quality one. Same with the plugs. I would also put two bottles of Chevron Techron fuel system cleaner in when you fill up with gas. Then take a very long drive.

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