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    5.0 Issues figured out?

    I think I know why my 5.0 is running bad (I know I'm building the 351 for it but I'd like to at least make this engine somewhat reliable for now). Anyway, It doesn't idle well (it bogs and surges and eventually dies). I thought it might be the IAC, but it was replaced within the last year or so. When I give the car just a little pressure on the gas pedal, it runs pretty smooth. Once I try to take off, It will start moving, then bog and die if I don't give it a lot of gas. Another thing that I noticed was that there is excessive carbon buildup in the exhaust. There is so much, that when I rev the engine, it throws chunks out the tailpipe and leaves a black mark on the pavement. I have replaced the spark plugs, cap & rotor, plug wires, and the fuel filter. I think it can be narrowed down to either a bad ignition coil or multiple bad injectors (has happened to me before with another car). I would scan it for codes, but nobody I know around here has an OBD-I scanner. I may ask around some more tomorrow, but I am doubtful. So, what do yall think.


    2004 Crown Vic LX (Sold)
    1994 Lincoln Town Car
    2002 F250 CC 4x4 Diesel

    #2
    You can actually listen to the injectors and see if there are any dead ones. If you have a metal rod of some sort you can push the rod up against one injector and the other end at your ear and the noise from the pintle shooting will transfer through the rod to your ear. Like a stetheskope, but easier to manuver under the depths of the intake plenum. Compare the injectors with each other and you may hear some weak ones, or ones that are not firing at all.

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      #3
      The injectors are fairly easy to replace in these cars also and just buy the ones you need for now as your building another motor. You can also check your plugs to see which injectors are failing or not firing. Ex. excessive carbon buildup/blackened plug on #1 means its running rich on that injector, bright white on #4 means its running lean on that injector.

      From the description, it sounds like your car is running excessive rich, which can be from a few things. Check all of your vacumm lines, running this rich would be a major vacuum leak. Disconnected brake booster lines or upper intake vacuum lines will cause this type of problem. Map sensor to the upper intake is another to check. If that doesn't help, I would really lean towards a faulty map sensor or a failed FPR. Check your codes with a code scanner, I've seen some parts stores sell them for as cheap as $25 for all 82-92 fords.
      Last edited by 87mefull; 09-25-2006, 01:13 AM.
      Current rides - 1991 Ford Thunderbird 3.8 v6 (gas saver/DD) - New Heads/Headgaskets with ARP studs, Air Silencer Delete, 70mm MAF, Plasti-dipped Matte Black with a Silver Metalflake Overlay, Muffler Delete, some LED's, 30.233 MPG for high MPG average!
      2006 Jeep Wrangler 4WD (fun vehicle/backup DD) - 4.0/6spd - too many mods to list.

      Associated Panthers:
      Father's 1994 Ford Crown Victoria - Stock, 45,000 miles.
      Sold in 2007 - 1987 Mercury Grand Marquis LS "Grandpa Special" 2 door.
      http://www.cardomain.com/ride/2128327

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        #4
        If its stumbling and running super rich I'd have to suspect massive vacuum leak somewhere. How do your vac hoses look? If the MAP sensor isn't recieving the vacuum signal it expects, it will pump more fuel into the motor assuming it is under high load. You should also pull the vacuum hose off the fuel pressure regulator. If it is wet with gas, replace the regulator. If you have a vac guage, hook it up somewhere to a vacuum line straight off the manifold and see what you're reading. It should be 17" or more if the engine and vacuum system is working properly.
        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

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          #5
          I run 18" of vac at idle in drive, and 22" of vac in park or neutral... seen 26" on down hill decent at 70+mph in OD at 0% throttle.... normal cruise at 65-70 is between 13-10" I disconnected my MAP vac line while it was running, killed it immideately
          1987 MGM 126K 2" True Duel flowmaster 40's 3" tipped exhuast, Tinted 20% all way round, individual bank A/F guages, tach.

          Comment


            #6
            How do you get the map vacuum line out of the back of the intake? Is there a trick to it, or do I have to take the whole intake apart?


            2004 Crown Vic LX (Sold)
            1994 Lincoln Town Car
            2002 F250 CC 4x4 Diesel

            Comment


              #7
              Pull the upper intake off, vacuum lines are easy to access then. 6 bolts for the upper intake, 2 are under the 5.0 plate.
              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
                Alright, thats what I was afraid of. Oh well, now I got a project for Sunday.


                2004 Crown Vic LX (Sold)
                1994 Lincoln Town Car
                2002 F250 CC 4x4 Diesel

                Comment


                  #9
                  The exact same thing happened to mine last month.Replacing the Map vac line under the intake solved the problem.If the vacuum line going to the map sensor is broken you should be able to hear a hissing sound that will be audible above the sound of the engine.

                  Comment


                    #10
                    Originally posted by LtMercDaddy
                    I run 18" of vac at idle in drive, and 22" of vac in park or neutral... seen 26" on down hill decent at 70+mph in OD at 0% throttle.... normal cruise at 65-70 is between 13-10" I disconnected my MAP vac line while it was running, killed it immideately
                    22" at idle out of gear is excellent. You probably get pretty good fuel economy too don't you? High manifold vacuum at idle in a stock motor generally means its in good operating condition. When its low, and/or unstable it means there is a problem.
                    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


                      #11
                      Well, after changing the vac line to the map sensor, the car runs perfect. My brother even volunteered to change the vac line in his auto mechanic class.


                      2004 Crown Vic LX (Sold)
                      1994 Lincoln Town Car
                      2002 F250 CC 4x4 Diesel

                      Comment


                        #12
                        good to hear its fixed

                        Originally posted by gadget73
                        22" at idle out of gear is excellent. You probably get pretty good fuel economy too don't you? High manifold vacuum at idle in a stock motor generally means its in good operating condition. When its low, and/or unstable it means there is a problem.


                        Yea,I consistantly run 20+ mpg running with 3.27's and std tires.... seen 25mpg using a light foot... thats with 87oct too...
                        1987 MGM 126K 2" True Duel flowmaster 40's 3" tipped exhuast, Tinted 20% all way round, individual bank A/F guages, tach.

                        Comment


                          #13
                          Originally posted by mattgw86
                          Well, after changing the vac line to the map sensor, the car runs perfect. My brother even volunteered to change the vac line in his auto mechanic class.
                          Awesome. Now, let's break it.
                          ...seems to be all I know how to do.
                          2011 Mustang GT Premium, MT82, Kona/Saddle, HIDs, 3.73s, 19s, hood/side stripes, UPR 1.5" springs with adjustable panhard bar, and UMI solid LCAs and relocation brackets.
                          1992 Explorer Eddie Bauer, slight lift, 34s, and A/C...
                          1979 Bronco Custom, 351M/C6/NP205, 4" lift, 35s, lots of fender trimming.

                          Comment


                            #14
                            Originally posted by Freshmeat
                            Awesome. Now, let's break it.
                            ...seems to be all I know how to do.
                            Just give it time, I'm sure I'll break something else soon.


                            2004 Crown Vic LX (Sold)
                            1994 Lincoln Town Car
                            2002 F250 CC 4x4 Diesel

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