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84 Grand Marquis with engine stutter while cruising

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    #46
    I checked again and the car will not even think about starting with the ECT unplugged. I don't know which is the choke so I didn't try wiring it open, but it wouldn't fire at all even while pumping the throttle.

    Having second thoughts about the plug wires since plug wires shouldn't work fine for approximately 3 minutes and then decide to act up. Wires are just wires, either they work all the time or they foul all the time, unless they're arcing, but again they'd arc all the time, possibly randomly, but not only and specifically after 2 or 3 minutes of running.

    Pulled out the ECU which was much easier than expected. Everything inside looked immaculate, like it was brand new. The warranty stickers were still intact so it'd never been tampered with. Sorta felt bad cutting them. There are three Nichicon capacitors which look to be in perfect condition. I took some pictures with a real camera if anyone is interested for historical/archival purposes. I didn't take the main board out of the ECU housing because there's a daughter board attached with a ribbon cable, and that ribbon cable seems almost as if it's made out of paper, so I just carefully put it back together and put it back in the car.

    I unplugged the O2 sensor because someone in another thread said that their car always ran better with it unplugged. It didn't make a difference here. Just gave me more time to verify that the car runs perfectly for 2 or 3 minutes after starting and then the stutter begins.

    And then it started to stall again. Luckily it was right as I pulled into the driveway. Had to keep my foot on the throttle just to get it parked out of the way of the other cars. I'm guessing that whatever is causing the stutter is also eating the TFI because I bet if I change the TFI again it'll stop stalling again.

    I'm also wondering if whatever is causing the stutter is related to closed loop vs open loop mode since it begins to stutter at about at the point where it should be changing to closed loop. Or maybe it's something entirely different since it keeps eating TFI modules.

    Comment


      #47
      It doesn't have a choke exactly, it just has a high idle system that uses most of the same parts carb chokes did use. Its the hockey puck thing on the side of the CFI unit. There is also a vacuum doo-dad back there. The hockey puck is a heater with a spring in it. The vacuum thing is the choke pull-off, even though there isn't technically a choke flap. When cold, the spring pushes the high idle cam down so you get high idle on cold start. The vacuum thing tries to lift it back out. As the spring heats it gets weaker until the vacuum pull-off can overcome it and lift the high idle cam out. Thats all it does, it doesn't affect fuel mix or any of that. Just makes the engine cold start a bit easier.


      Does it do the stuttering and carrying on at idle when not driving? That makes troubleshooting somewhat easier. if it does, will unplugging the SPOUT connector make it quit acting up? Have you ever checked it for codes? I'm wondering if its got either a PIP or an IDM code.


      Look close around the legs of the caps. The last few I've been into, the caps looked like a baby with an over-loaded diaper. Brown-green goo oozing down the legs. A quick poke with a q-tip dipped in rubbing alcohol will confirm it. If it comes away clean, the caps aren't leaking physically. Brown stains need replacement. For whatever reason it seems like the cap that is further away from the connector gets oozier than the other 2.

      The car I dealt with that had bum wires would idle and run fine under light load. Up hills was bad, full throttle was fine, steady cruise had a random misfire but nothing alarming. I seem to recall it was a bit worse warm but it did not go from normal to bad suddenly like you're describing. I do remember that car had a bum O2 sensor. Didn't affect how it ran at all, it just cut the fuel mileage about in half.
      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


        #48
        Originally posted by gadget73 View Post
        ...Look close around the legs of the caps. The last few I've been into, the caps looked like a baby with an over-loaded diaper. Brown-green goo oozing down the legs...
        1985 LTD Crown Victoria - SOLD
        1988 Town Car Signature - Current Party Barge

        Comment


          #49
          It doesn't stutter at idle when it's acting up (the stalling from the TFI doesn't count), but the idle isn't steady, it wavers just a bit, and it's always high, and sometimes there's a slight miss, like a fraction of a miss. Also feels like there's more vibration in the fenders. Unfortunately these are all somewhat slight effects at idle. To really tell I have to drive it for a couple minutes, then it's readily apparent.

          Unplugging the spout doesn't seem to make a difference at idle. If the TFI will behave today I'll give it another shot and pay closer attention. I never checked for codes, but I imagine it's got some now since I ran it with the o2 sensor unplugged. Is it possible to pull codes without a scanner like on OBD1 Chevys?

          I checked the caps pretty well, no oozing of any sort, even the one in back, which was a little harder to see. The tops were flat and they looked very good all around. I have some experience with bad caps, and even caps that look perfect can have issues, as was the case on the last recap project I did, but seeing as how these are Nichicon I think it's safe to say that they're still good. Here's part of the pictures I took. It was easier to see the bottom of the caps than it was to take pictures. Gotta love the bokeh effect in the shot with the two up front.

          Click image for larger version

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          Comment


            #50
            You can check the codes like so:
            http://www.grandmarq.net/oldfuelinjection/page13.html

            Skip to the test light section, your engine light won't blink.
            I did mine with screwdriver-type test light. I'd also recommend videoing the blinking so you can rewind and rewatch as many times you please.
            1985 Mercury Grand Marquis LS, "Maisa"
            1995 Chevrolet Caprice Classic STW, "Sally"

            Comment


              #51
              Is the idle set properly? Is it coming off the high idle cam? High idle could be a vacuum leak if its not just mechanically adjusted wrong. Some amount of idle control is done with the timing advance, but if pulling the SPOUT does nothing, I'm thinking that isn't why its high. Usually that will make the idle rpm drop. Unless its just set too far advanced because the balancer spun, which is not impossible either.

              If the codes tell you nothing, maybe confirm TDC is where you think it is. Pull #1 plug and poke a screwdriver in there. Rotate the engine until the screwdriver is as far out as it goes. There is a small amount of crank rotation where the piston won't move. Right in the middle of that is TDC. If the balancer is way off it probably spun and ought to be replaced. If its just a few degrees off, you can re-mark it and make a new 10 BTDC mark from that point.
              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


                #52
                Sorry, I should have been more specific. It always idles high when it's doing the stutter, even when it's plenty hot. When it's behaving properly for that 3 minutes, the idle is as it should be.

                Confirmed another dead TFI today. Engine stalls and bucks every time it starts now, unplugged the spout and it quit stalling. Drove it with the spout unplugged and it still stuttered, though it was exacerbated somewhat by the massive lack of power.

                I'm pretty sure the base timing is correct because it has plenty of power when it runs correctly. It'll do a brake stand/power brake and spin a tire pretty easily when it's not in stutter mode (found that out on accident).

                I'll check the codes tomorrow, have to find some spades to stick in the test terminals.

                Comment


                  #53
                  what voltage does it charge at? No reason you should be cooking ignition modules. Wondering if its high voltage or maybe a partially shorted ignition coil. Either would abuse the TFI.

                  use a timing light and confirm its right, these don't really respond quite right to carb adjustment methods. SPOUT unplugged when checking.
                  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


                    #54
                    It shows 14.43 volts at the battery while running, and the same at the positive junction on the fender. The only thing left in the ignition system that hasn't been changed is the coil, and it's a bit rusty. Maybe it's arcing/leaking current internally?

                    The timing was good the last two times I checked it, at least it was dead on with the previous paint mark on the crank pulley. I'll have to see if I can make the original indication marks visible so I can read the degrees. They're not currently readable due to surface rust and dirt.

                    I got one KOEO code which is,

                    23 - Closed throttle TPS voltage higher or lower than expected.

                    Then I got multiple stored or CM codes, 14, 18, 22, 31, 41, 51, 54, and 63.

                    14 - says erratic PIP resulting in a possible engine miss or stall.
                    18 - is IDM circuit failure or spout grounded, so that answers your question about those two @Gadget73.
                    22 - is for the MAP sensor, the shop saw that one before and put in a new NAPA MAP sensor.
                    31 - looks like EGR related, and the shop had also replaced that.
                    41 - says HEGO sensor lean right side, that's the O2 sensor? Maybe from when I unplugged it?
                    51 - is ECT sensor greater than self text max of 4.6v. That's the one that acted funny when cold but ok when hot when I tested it.
                    54 - is ACT sensor. I replaced that a week ago because it was all gunked up.
                    63 - is TPS intermittantly failed below minimum 0.6v.

                    I didn't do a KOER test, should I?

                    So according to this I should replace the TPS since there's two codes for that. Those look to be about $45.

                    I've tried starting the car with both temperature sensors unplugged (at different times) to see what would happen, same with the O2 sensor. Maybe a cause for some of those codes?. And once I forgot to plug in the TFI before trying to start it... not sure if that would cause one of those codes.

                    The code for the MAP and EGR were there before when the shop checked it a few months ago, but I disconnected the battery and let it sit overnight in the first week of troubleshooting (about the time I started this thread). That should have erased all the codes from what I read. Plus I just had the computer out of it a couple days ago, should that have erased all the codes again? Should I erase the codes now and see what comes back? Maybe after replacing the TPS?

                    I have an idea for the TFI. I have a large heat sink from an old computer CPU, it's exactly as long as the metal back plate of the TFI, and much wider. Should I make a small extension for the TFI and mount it to the heat sink for better cooling? I could probably even connect the old CPU fan and have that run. The distributor body looks to be rather terrible for heat dissipation. I'd probably leave it in the same location by the distributor, just with three short leads to connect the TFI to the distributor, maybe 3 or 4 inches long. I'd make it longer to put it somewhere cooler, but the original harness won't stretch very far and I don't feel like taking the harness apart at this point. I figure it's gotta be better than trying to get rid of heat through the distributor body. Good idea or bad?

                    Comment


                      #55
                      Check both the main ground cable from the battery to the block for breaks and the ecu ground from the battery. After reading over the thread I can only think that its maybe a ground issue.


                      Sent from my iPhone using Tapatalk

                      Comment


                        #56
                        Check the TPS and see if it gives you close to these voltages at the bottom of the page: http://www.grandmarq.net/oldfuelinjection/page30.html between the green and black wire. You’ll have to pierce the insulation on the wires.

                        Removing the computer should have cleared those stored codes. I highly doubt all those sensors have/had issues unless it is a ground/power issue as mentioned.
                        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

                        Comment


                          #57
                          IDM is the circuit from the coil back to the ECM. It goes through a resistor. If you unplug the coil and the ECM, you should be able to measure ~22k ohms from the coil - terminal to pin 4. What that does is confirm to the ECM that the spark advance it commanded is actually happening. If the resistor is bad you'll get problems with this. A bad TFI might also do this if its not responding to spark advance commands. Also possible that the test with the SPOUT unplugged caused it, not 100% on that.

                          PIP signal is the pickup in the distributor. Bad one or bad TFI can cause that. Honestly not surprised to see either of these considering the history here but its nice to confirm the ECM has some idea of whats going on.


                          The ECT, ACT, TPS, EGR, and MAP sensor all rely on the same 5v and ground references. Might be worth measuring on the TPS from black to orange to see what you get. If its not in the 4.5 - 5.5v range, thats why all this has gone bonkers.

                          and yeah all those codes should have cleared when the ECM was unplugged so it seems all that stuff has set since that point.
                          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


                            #58
                            How many miles on the car? Any oil leaks from the valve covers?
                            '79 Continental Town Car
                            '90 Crown Victoria LTD
                            '94 Crown Victoria

                            Comment


                              #59
                              I'm back! I bet you guys thought I solved the problem and then just disappeared. I'm not a jerk like that, and unfortunately no, I didn't solve the problem. It just got too hot here in Florida to work on the car very much over the summer. I did check on several things when it wasn't 100 degrees and/or raining.

                              To recap so you don't have to scroll up too much, the car runs perfect when it first starts up... for a couple minutes, then it goes to stuttering, sometimes it stalls. With lots of throttle it's fine, but it could possibly be slightly down on power compared to when it's running perfect. At parking lot speeds after it's been running a while it makes you worried if you're going to get into a parking space before it dies. When cruising at 45 or so you feel a light to medium hesitation/stutter that's sorta constant, but not 100% constant, more like if a cat were batting at your main coil wire. The weird part is that if you shut it off then start it right back up, it once again runs absolutely perfect... for a few minutes. This can be repeated consistently.

                              Originally posted by Tiggie View Post
                              Check the TPS and see if it gives you close to these voltages at the bottom of the page: http://www.grandmarq.net/oldfuelinjection/page30.html between the green and black wire. You’ll have to pierce the insulation on the wires.

                              Removing the computer should have cleared those stored codes. I highly doubt all those sensors have/had issues unless it is a ground/power issue as mentioned.
                              I checked the TPS and the voltage swing from closed to open throttle is good and even. However, according to that link, closed throttle voltage should be 0.6 to 1.0 volts and it's showing 1.76v at closed throttle, with the engine off. I think it got up to about 4v at fully open throttle. Could the 1.76v at closed throttle be part of the problem? Keep in mind that the engine runs perfect for a few minutes before it starts acting up. I still think it has something to do with open loop vs closed loop mode and when it's running perfectly it's in open loop mode then it starts to act up when it goes to rely on the sensors in closed loop mode. But doesn't the TPS affect open loop as well as closed loop?

                              Originally posted by gadget73 View Post
                              IDM is the circuit from the coil back to the ECM. It goes through a resistor. If you unplug the coil and the ECM, you should be able to measure ~22k ohms from the coil - terminal to pin 4. What that does is confirm to the ECM that the spark advance it commanded is actually happening. If the resistor is bad you'll get problems with this. A bad TFI might also do this if its not responding to spark advance commands. Also possible that the test with the SPOUT unplugged caused it, not 100% on that.

                              PIP signal is the pickup in the distributor. Bad one or bad TFI can cause that. Honestly not surprised to see either of these considering the history here but its nice to confirm the ECM has some idea of whats going on.


                              The ECT, ACT, TPS, EGR, and MAP sensor all rely on the same 5v and ground references. Might be worth measuring on the TPS from black to orange to see what you get. If its not in the 4.5 - 5.5v range, thats why all this has gone bonkers.

                              and yeah all those codes should have cleared when the ECM was unplugged so it seems all that stuff has set since that point.
                              I didn't check the ohms between the coil to pin 4 yet because I forgot to put that on the list. But I did check the voltage at the tps orange wire to ground and it was at 5.03v and steady. I may go back and check it again while the engine is acting up to see if it changes.

                              I also checked the coolant temp sensor and since it was reading a little funny at the lower end I replaced that. No change. So now both temp sensors are new. I also ran it without the alternator hooked up to see if perhaps the alternator was giving off spikes or "dirty power" but no, it acted the same while running off just the battery.

                              I will see about checking the ohms from the coil to the ecu tomorrow. Oh, and it has 130,000 miles on it, no oil leaks.

                              Comment


                                #60
                                Well, I loosened the TPS and the lowest it registers is 1.38v, no matter how far backwards I turn it. I took the TPS off entirely and it still registers 1.38v. Does that mean it's bad, or is this just how the 1984 version behaves, because I noticed that all of the guides I've seen so far are for 1986 to 1990 something.

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