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Thread: 84 Grand Marquis with engine stutter while cruising

  1. #41
    I'm an air-conditioned gypsy gadget73's Avatar
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    ECT sensor could be flaky when cold.

    Last 84 I fooled with that did stuff like this, we chased all the usual stuff. Ended up being the nearly new spark plug wires. Stuck a used set of Ford Racing wires that i had pulled from my car on and it ran like a watch. That one would carry on mostly under load. Going up hills made it really unhappy.

    I wouldn't completely rule out sloppy timing chain either. Pull the cap off and rock the crankshaft with a breaker bar. If you can move the crank any real amount before the rotor starts to move, thats not good. 84 has that plastic cam gear and they get really sloppy as the plastic wears down.

    The ECM is in open loop until it sees ECT at 160 for some amount of time. Hot restarts will be open loop for a minute or so until it settles out.

    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

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  2. #42

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    The spark plug wire bit strikes a cord because it wasn't doing the stuttering bit before I changed the TFI (the first time) and spark plug wires. At least not that I remember, and I think I'd remember this herky-jerky stuttering. I'd put the old wires back on but two of them came apart when I took them off, which is why I replaced them. Maybe I'll see about fixing those two and putting them back on. I don't understand how it could run perfect for about three minutes due to plug wires. Same for timing chain slop. Both seem like something that should affect the engine all of the time, not just after a couple minutes. I'll check them anyways though. I'll see about checking the ECU as well and those caps that leak on some people.

  3. #43
    I'm an air-conditioned gypsy gadget73's Avatar
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    What wires did you use? I seem to remember the problem ones were new Belden from Napa. Oddly I had the same ones on my black Mark VII and never had issues with them. Might be one of those spots that boring old Motorcraft wires are the answer. They're only like 30 bucks new from Rockauto.

    Just did an ECM tonight, in 1990 at least its a pair of 47uf 16v and a 10uf 63v. It had the same leaky cap mine had. Not sure if the CFI computers are different, I expect they are just because why wouldn't they be? Fuzzy memory says Kishy posted pics of some CFI computer internals a few years ago.

    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

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  4. #44

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    The wires I got are "Accel Custom Fit Super Stock" from Advanced Auto. The ones that were on it were "Accel Universal Fit Super Stock" which were much longer with straight boots instead of the angled boots. With cars like this I try to avoid buying things online because of the hassle of returns/warranty replacements. Getting the TFI replaced twice was cake at the parts store. Seems that my local Advanced Auto only carries Accel, MSD, Driveworks and Carquest. Autozone has the same Accel and MSD plus Bosch and Duralast.

    It seems the CFI computers do have similar caps. I found a forum post elsewhere about an 84 Mustang LX 5.0 with factory CFI and they mentioned the caps in the ECU, couldn't find much info on whether they often leak or not.

    As a side note, the car wouldn't start with the coolant temp sensor unplugged, and it wasn't a very happy camper after plugging it back in either.

  5. #45
    Wagon Addicted Tiggie's Avatar
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    An SEFI car will start and run fair enough to drive with the ECT unplugged. I don’t know if CFI is suppose to or not, but I would suspect it should.

    I wonder what would happen if you wired open the choke?

    I have had those Accel Super Stock custom fit plug wires on my 88 for several years. No complaints.
    1988 Crown Vic Wagon - daily
    1990 Country Squire - weekend cruiser, former lawn ornament
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  6. #46

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    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.

  7. #47
    I'm an air-conditioned gypsy gadget73's Avatar
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    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 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

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  8. #48
    GMN Regular DerekTheGreat's Avatar
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    Quote 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

  9. #49

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    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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  10. #50
    Member Arquemann's Avatar
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    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
    1997 Volvo 850 GLE Estate

  11. #51
    I'm an air-conditioned gypsy gadget73's Avatar
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    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 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

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  12. #52

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    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.

  13. #53
    I'm an air-conditioned gypsy gadget73's Avatar
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    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 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

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  14. #54

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    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?

  15. #55

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    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.


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  16. #56
    Wagon Addicted Tiggie's Avatar
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    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.
    1988 Crown Vic Wagon - daily
    1990 Country Squire - weekend cruiser, former lawn ornament
    Other: 95 Ranger, 74 F250, 68 Mustang, 94 Mustang
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  17. #57
    I'm an air-conditioned gypsy gadget73's Avatar
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    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 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

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  18. #58
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    How many miles on the car? Any oil leaks from the valve covers?
    '79 Continental Town Car
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    '94 Crown Victoria
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    You may regret selling it. Think it over.

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