Engine - Occasional runaway idle | Ford Escort Owners Association (FEOA)
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Engine Occasional runaway idle

Discussion in '2nd Gen 1991-1996 1.9L SOHC' started by Chick Magnet, Feb 7, 2017.

  1. Chick Magnet

    Chick Magnet FEOA Donator

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    This problem may or may not be related to another problem I am having:

    Link

    Annoyingly, this problem is intermittent. Sometimes the car will start to increase idle speed, up to 3K or more. I can go days without it occurring, other times it happens regularly on the ride to/from work. Often I can fix it by turning the ignition off and back on. This workaround seems more successful if I do this with high vacuum, e.g. engine braking conditions. What I mean by that is if I can tell it's doing it's high idle nonsense by its behavior during gear changes, I'll put it in the lowest appropriate gear for my speed, let out the clutch and turn the ignition off for a second or two and back on.

    I have looked through this thread and found no help. I have checked all potential vacuum leaks, replaced the soft parts of the PCV plumbing, etc. The ISV moves freely, and I have a spare ISV that my brother put a plexiglas window on to check the function. Problem occurs with either ISV.

    The one thing I suspect at this point is the brake booster. I have noticed that the problem occurs most frequently if I am very light on the brakes coming to a stop. Sometimes fiddling with the brake pedal makes the idle increase more rapidly. I can't get the car to do this in my driveway and, living in the mountains I am not anxious to try disconnecting the brake booster for long enough to be sure. I can test by putting a 12V solenoid valve in the brake booster vac line and closing the valve to see if that fixes it, but I thought I would see what the hive mind says before I go to that expense and effort.
    Last edited: Feb 7, 2017
  2. denisond3

    denisond3 Moderator Staff Member

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    I had similar symptoms, and unplugged the control line to the EGR valve. No such symptoms since that time - so I figured it was a sticky EGR valve. I will replace the valve eventually. For the time being, it makes the "Check Engine Light" come on, but it wont have to pass the emissions test until october.
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  3. Chick Magnet

    Chick Magnet FEOA Donator

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    I've tried disconnecting the EGR line and plugging it, it has no effect on this issue. Thanks for the response though.
  4. FordMan59

    FordMan59 FEOA Member

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    When I had this problem with my '88 Pony it was a bad ECU. I would remedy the problem the same way you are by turning off the ignition and restarting. Finally it got to the point it was doing so often something had to be done. I found an Escort that still had the ECU in it and as it worked out that Escort was going to the junk yard that day. The owner said if I'd remove it I could have the ECU. The ECU on your 2nd generation is located behind the passenger side kick panel of the console.
  5. Chick Magnet

    Chick Magnet FEOA Donator

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    Thanks FordMan. I found an ECU for $15 shipped on ebay, great warranty/return policy/feedback. Probably the cheapest/easiest thing to try.
  6. Pizzaman5000

    Pizzaman5000 FEOA Donator

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    That only works as long as the egr isn't leaking exhaust gases. Egr problems are sneaky on escorts. Personally I'd electronically disable the dpfe before plugging the vacuum line. I have seen a leaking egr myself, it was carbon, and never stuck after cleaning.
  7. Chick Magnet

    Chick Magnet FEOA Donator

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    Normally I expect the idle to drop rather than increase with EGR flow -- another reason I didn't suspect this. Will double-check. I didn't suspect the EGR because the engine idle drops(from normal idle) with the least amount of vacuum applied to the EGR valve. If I apply pressure idle doesn't change. It's possible it sticks intermittently.
  8. Pizzaman5000

    Pizzaman5000 FEOA Donator

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    It CAN act like a vacuum leak, but with egr, the timing goes nuts, and can cause an idle increase. Sometimes.
  9. Chick Magnet

    Chick Magnet FEOA Donator

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    Great info, thanks. I'll dig into this over the weekend. For now -- living in the Santa Cruz mountains sans garage -- we're battening down the hatches for the next storm. :/
  10. FordMan59

    FordMan59 FEOA Member

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    With the ECU check to see if it looks like there's been any water on or in it. I think I remember someone on the forum saying sometimes the heater core of the second generation can leak onto the ECU if it's leaking. If it looks like it's been wet you need to repair the problem prior to installing the new ECU to keep it from damaging the new one. When I had the problem with my '88 Pony the idle would go high enough that I could drive down the road without my foot on the gas and continually gaining speed. As soon as I'd turn the ignition off then restart the engine the problem would be resolved until it decided to do it again whether it was 5 minutes or 5 days later. When mine began it was only occasionally, but by the time I fixed it it was doing it several times a day. If the problem is the ECU it will get worse with time.
  11. millball

    millball FEOA Donator

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    I once had this issue on a 1993 1.9 with no EGR and a new throttle position sensor fixed it.
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  12. Pizzaman5000

    Pizzaman5000 FEOA Donator

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    I am starting to agree on a tps too
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  13. Chick Magnet

    Chick Magnet FEOA Donator

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    I know that this car has had a heater core leak, a repair, then another leak when my brother owned it. So, the first thing I'm going to do after the replacement ECU arrives is drop that in, checking and cleaning the connector and ground in the process... then see what symptoms remain.

    I didn't get to any car stuff this weekend. When I saw your note I realized that I really need to check this first. I've been busy with local infrastructure and storm mitigation.

    Things have been... interesting in my local area. This is what would normally be my second alternate route to work looks like. My main route is closed due to slide and my alternate is now the only route.

    SkylineWashout_Pano_smaller.jpg
  14. Chick Magnet

    Chick Magnet FEOA Donator

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    I think my brother replaced that at least once, and I have two spares that check out. Once the ECU is in I will see where I stand, and check this. In the other thread(linked in OP) I noted the connection of TPS to EGR; It's definitely high on my list to check.
  15. FordMan59

    FordMan59 FEOA Member

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    I can't say with certainty the ECU is the problem, but I do know that was the problem with my Pony. If there's been a previous heater core leak I'd say that probably also increases the likely hood of the ECU being the problem. Good luck and keep us informed of the final outcome.
  16. Chick Magnet

    Chick Magnet FEOA Donator

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    Sure, I get it. But for $15 it's worth a shot. :) Will update as I move forward. Thanks again for the help!
  17. Intuit

    Intuit FEOA Member

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    I've experienced the intermittent racing engine before and it was a dirty idle air control solenoid.
    https://www.feoa.net/threads/cleaning-the-iac-solenoid.71349/

    1st Gen problems with the ECU are due to bad capacitors. You can replace the capacitors without replacing the ECU.
    https://www.feoa.net/threads/1-9l-cfi-—-video-inside-fuel-injection-issue-solved.81288/#post-722475

    2nd Gen problems with the ECU are rare to non-existent; with the exception of having been leaked-on or zapped by shorting wires. Users reported that the ECU would return to normal operation once dried out.

    .

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