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    99 MGM engine miss fire

    i did a scan on my friends 99 merc LS. threw a CEL and runs rough in higher speeds so, i scanned it and P0304 comes up-cyl #4 miss fire detected. now not to sound like a n00b(cuz im far from it lol) witch side on the 4.6L is cyl #4? what should i check other than compression and plugs? how do i test the #4 coil? all help is appreciated.

    1981 Mercury Marquis Brougham 2-Door 302/ 5-speed -special blend (GMGT)
    1987 Lincoln Mark VII 5-speed (Errand runner)
    1989 Mercury Grand Marquis (Base Runner)
    2007 Lincoln Town Car Signature Limited (Hustlyn)
    2011 Ford Crown Victoria Police Interceptor (Down with O.P.P)

    #2
    would this http://www.allworldauto.com/tsbs/NHT...in_130109.html have somethin to do with it?

    1981 Mercury Marquis Brougham 2-Door 302/ 5-speed -special blend (GMGT)
    1987 Lincoln Mark VII 5-speed (Errand runner)
    1989 Mercury Grand Marquis (Base Runner)
    2007 Lincoln Town Car Signature Limited (Hustlyn)
    2011 Ford Crown Victoria Police Interceptor (Down with O.P.P)

    Comment


      #3
      Looking at the engine From passanger side-Radiator to fire wall its 1234 The from DR side rad to firewall its 5678. remember this is NOT the firing order its the cylinder #...I have no idea why its different.

      So your friend has a misfire in the plug closest to the heater core hose nipple in the manifold.

      As for checking COPS, If you have an Ohm meter.Probe one Male pin on the COPand probe the spring...Anything over 5 ohms is good.

      Dear god I hope its not a coolant leak at that nipple...That sux.

      Also you can check with a regular old 12v test light the two-Female ignition connector that plugs into the COP. ... while the engine is running, Remember the coil generates the BIG spark so its cool to test the wiring ..leave COP in its place...Just unplug the connector ONLY.

      Look for a pulse on one side and a steady on the other,This will verify that the coil is getting the right juice the right way.
      Last edited by Rizzo; 12-17-2008, 03:01 AM.

      Comment


        #4
        well i noticed that it has a slight coolant leak on the rear pass side of the engine around the stated cyl #4. looks like the intake and is an external leak.

        1981 Mercury Marquis Brougham 2-Door 302/ 5-speed -special blend (GMGT)
        1987 Lincoln Mark VII 5-speed (Errand runner)
        1989 Mercury Grand Marquis (Base Runner)
        2007 Lincoln Town Car Signature Limited (Hustlyn)
        2011 Ford Crown Victoria Police Interceptor (Down with O.P.P)

        Comment


          #5
          needs a manifold.

          there's a fitting back there with a coolant hose attatched to it and the fitting is leaking. go get a dorman.

          will also need that plug and probably the COP

          as for why there's a difference between cylinder identification and firing order, it's a Ford, it makes sense. It's actually easier to identify the cylinders seperate from the firing order so that there's consistency between the engines in cylinder identification. the front most cylinder is always #1, then it goes sequentially along that bank then continues with the front cyl on the next bank. That works for all of fords engines
          GMNRadio DJ, Podcast Co-Host
          1984 Ford LTD Crown Victoria - Drag Car.
          99 Ranger 2.5 - Parts hauler and Pit truck.
          03 Mustang 3.8 Convertable - Head Gaskets fukered up
          95 S10 93 Accord

          Comment


            #6
            Thanks sneeb...The more ya know.

            Inspect the COP real good. If its hair line crack free then maybe just drying out the plug hole will do the trick. If you look at the "L" shape on the COP look at its 90* wrap under the round part, Thats where I developed some fine cracks.

            Dielectric grease is your friend. I about damn near iced mine like a cake after I replaced them. The L ,The boot top @ coil, The boot bottom @ spring...Man I went crazy.

            Comment


              #7
              i never really dealt with many of the newer 4.6Ls so this is good to know...and thanks for all the help, tomorrow ill go over and take a look at the situation lol

              1981 Mercury Marquis Brougham 2-Door 302/ 5-speed -special blend (GMGT)
              1987 Lincoln Mark VII 5-speed (Errand runner)
              1989 Mercury Grand Marquis (Base Runner)
              2007 Lincoln Town Car Signature Limited (Hustlyn)
              2011 Ford Crown Victoria Police Interceptor (Down with O.P.P)

              Comment


                #8
                Cool beans man....Lemme know how it turns out.

                Comment


                  #9
                  we, after all this time, buddy got parts for the merc. changed the COP on cyl#4 and threw in a set of plugs. when i removed the cop, i saw what sneeb was taking about, the cracked area around a brass fitting for the heater core. i temperarly pached it with some magic stuff that seems to hold for now. the car runs like a watch once again witch is good. now my question is, does the manifold have to be changed? or can i do a repare? the crack is very small and seems to puke a bit of coolant on high RPMs...thnx in advance.

                  1981 Mercury Marquis Brougham 2-Door 302/ 5-speed -special blend (GMGT)
                  1987 Lincoln Mark VII 5-speed (Errand runner)
                  1989 Mercury Grand Marquis (Base Runner)
                  2007 Lincoln Town Car Signature Limited (Hustlyn)
                  2011 Ford Crown Victoria Police Interceptor (Down with O.P.P)

                  Comment


                    #10
                    you might be able to get away with it for a little bit, but IMHO, it needs to be changed soon. ive changed a few already. dont forget new intake manifold gaskets.
                    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


                      #11
                      The Manifold gaskets are meant to be reused if they are not damaged.

                      If they are F'ed up,Try NAPA...They have a good set...I believe they sell FEL-PRO

                      Comment


                        #12
                        Originally posted by AKA_Rizzo View Post
                        The Manifold gaskets are meant to be reused if they are not damaged.

                        If they are F'ed up,Try NAPA...They have a good set...I believe they sell FEL-PRO
                        Its worth it just to replace the bitches while your in there.


                        Replace the intake with a newer aluminum crossover one. You can upgrade to the PI intake, alas you have to do some port matching with RTV IIRC. Something to look into.

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