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1987 MGM wagon stalls while driving or idling

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    1987 MGM wagon stalls while driving or idling

    Just bought a 87 MGM wagon over the weekend. It's got issues. The biggest one being it stalls out while idling, or driving. I replaced the battery, and starter for an unrelated issue. But replace the idle air control valve in hope it would fix the stall. In short, it didn't. I used volt checking light between the ignition coil and the distributor cap to see if the power cuts out when it stalled. After about 5 mins it arched through my hand and eventually it stalled. Hmm...maybe I was getting careless with my hand position? With a sore hand, I tried again. After about 5 mins, it did it again. This time I'm SURE it wasn't me being sloppy and loosing attention. It zapped me right after the EFI seemed to kick into overdrive and increase the idle or cycle or something. I'm not sure if I'm any closer to solving my problem, but I am sure I'll be awake for another several hours after getting mildly electrocuted twice!

    Could I have a bad ECU or something? I ask because it starts right back up as soon I turn the ignition all the way off and then try to restart. Like a reset. If I just crank it without turning ignition off the whole way it doesn't start up. So air and fuel don't seem to be missing.

    Thanks all!

    Jeff97062
    Last edited by jeff97062; 03-24-2022, 12:44 AM.
    1987 MGM Wagon

    #2
    Check all your grounds. Make sure the orange wire (ground) is attached to the lower intake manifold. It seems like the coil is shorting to ground somehow.


    Sent from my iPhone using Tapatalk

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      #3
      A lot of the time when boxes stall out like that, it's related to the distributor- namely the PIP sensor in it or the TFI module. Especially if it runs great but then dies out of no where. If it was a fuel starvation issue, it would sputter before dying. You could also verify fuel pressure before and after it stalls. Should be 35 to 40psi if I recall right.
      1985 LTD Crown Victoria - SOLD
      1988 Town Car Signature - Current Party Barge

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        #4
        Both above suggestions are sound. Do check ALL grounds but I'm betting on a dizzy issue/TFI.
        What I Own: 1993 Mercury Grand Marquis GS
        What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

        Comment


          #5
          +1 on suggestions so far. This is typically a heat issue with the ignition module on the side of the dizzy or the position sensor inside is losing signal. I had one where the dizzy was so worn out that the tone ring was wobbling enough to shave the PIP and had cut about 1/8 of an inch into the plastic and was probably starting to contact the metal of the sensor itself and cause issues. Replaced the whole dizzy on that one. I've also had TFI module on another do the heat up and die, cool off and run fine bit. Replaced that and as far as I know it's still running fine with the new owner. I've never had a dead coil act that way though, but if the plastic case is cracked, it's a good bet the coil is bad.

          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.

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            #6
            I'm going to throw an odd suggestion in, going a little against the grain...check the contacts of, and behaviour of the ECM power relay when wiggling the wires to it.

            The stall coinciding with a spark taking place outside of the cylinders definitely puts ignition components on the suspect list, but a sudden stall coinciding with a spark output has other possible causes, and especially in consideration of the no-start without cycling the key, I'm wondering about the "control side" of the stuff e.g. ignition switch and ECM relay.

            Current drivers: 84 TC | 85 CS
            Panthers, Parked: 83 GM 2dr | 86 GM | 88 TC | 91 GM
            Not Panthers: 85 Ranger | Ranger trailer | 05 Focus
            RIP: 97 CV | 83 TC | 04 Focus | Junkyards

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              #7
              Ford had a TSB for the TFI issue. Easy enough replacement but if you do, I would strongly suggest an OEM replacement only as I have personally found the others to be complete garbage. Also check the connector to it. I remember, several years ago, there was a company that was selling a heat sink with an extended harness so that it could be mounted on a wheel well (effectively taking care of the heat issue that was the issue). If you decide to go that way, I will try to find it, if they still exist! Of course if you decide to replace the entire dizzy, you get a "two for one" in that you would be doing everything at the same time. The suggestion on the ECM is also another avenue to pursue. Can't hurt, right?

              P.S. TFI relocation kit made by McCully Racing Motors.

              http://www.mccullyracingmotors.com/i...s/Page2271.htm
              Last edited by friskyfrankie; 03-24-2022, 04:48 PM.
              What I Own: 1993 Mercury Grand Marquis GS
              What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

              Comment


                #8
                +1 checking the ignition switch in the steering column. That is also a very common issue. Those like to disassemble themselves.

                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


                  #9
                  Originally posted by friskyfrankie View Post
                  Ford had a TSB for the TFI issue. Easy enough replacement but if you do, I would strongly suggest an OEM replacement only as I have personally found the others to be complete garbage. Also check the connector to it. I remember, several years ago, there was a company that was selling a heat sink with an extended harness so that it could be mounted on a wheel well (effectively taking care of the heat issue that was the issue). If you decide to go that way, I will try to find it, if they still exist! Of course if you decide to replace the entire dizzy, you get a "two for one" in that you would be doing everything at the same time. The suggestion on the ECM is also another avenue to pursue. Can't hurt, right?

                  P.S. TFI relocation kit made by McCully Racing Motors.

                  http://www.mccullyracingmotors.com/i...s/Page2271.htm
                  If you're into DIY: http://www.grandmarq.net/vb/showthre...tor-Conversion
                  Vic

                  ~ 1998 Mercury Grand Marquis LS - new DD
                  ~ 1991 Mercury Grand Marquis LS "The Scab" - plenty of rot, backup/summer cruiser
                  ~ 1997 GMC Yukon SLT - wannabe winter DD - many issues, returning sometime in the 2020s
                  ~ 1991 Mercury Grand Marquis GS "The Ice Car" - Rotting Retired Winter DD
                  ~ 1989 Mercury Grand Marquis GS - Rotting Retired DD
                  Gone but not forgotten:
                  ~ 1988 Country Squire ~ 1987 Ford Crown Vic

                  Comment


                    #10
                    How old are those ignition parts? Despite the "modern" EFI, its an engine designed in the 1950s and it still needs good plugs, wires, cap, and rotor to run properly. I'm sure I'm not the only one on here who has seen original 1980s wires in use long after they were done being properly useful.

                    Can usually trigger an ECM or fuel pump relay to act up by giving them a few whacks with a screwdriver. They live under the plastic covers near the washer bottle. Green is the fuel pump and brown is the ECM if I remember right. Black is AC cutout. The wiring to those sockets can get crusty too.

                    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 SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

                    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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                      #11
                      Update - thermo paste in TFI

                      Update - put thermo paste behind TFI. It made it better, but didnít fix. It still stalled eventually, just not as soon. It seems the TFI the previous owner put in it is cheap plastic crap. Actually, the whole distributor head looks like CPVC plastic junk. Should I not bother with relocating TFI and buy a more reputable distributor?

                      Iím a weekend warrior newb. More experienced opinions welcome!
                      1987 MGM Wagon

                      Comment


                        #12
                        Originally posted by jeff97062 View Post
                        Update - put thermo paste behind TFI. It made it better, but didn’t fix. It still stalled eventually, just not as soon. It seems the TFI the previous owner put in it is cheap plastic crap. Actually, the whole distributor head looks like CPVC plastic junk. Should I not bother with relocating TFI and buy a more reputable distributor?

                        I’m a weekend warrior newb. More experienced opinions welcome!
                        I would be replacing the TFI first. Not sure how reliable the Petronix TFI is in case you can't get an OEM. If after replacing it with a good unit and you still have the issue then look at the dizzy. DON'T go with Duralast or other local store garbage. Not sure what NAPA stocks so it is something to look into in case the search for Motorcraft comes up empty.
                        What I Own: 1993 Mercury Grand Marquis GS
                        What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

                        Comment


                          #13
                          I believe this is the correct OEM part but PLEASE verify if you decide to go for it.

                          https://www.ebay.com/itm/33423572623...sAAOSwKmNhpBuF
                          What I Own: 1993 Mercury Grand Marquis GS
                          What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

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